Semiconductor device and method for manufacturing the same

ABSTRACT

A first resist mask and a second resist mask used for forming a gate electrode for a p-channel TFT and a gate electrode for an n-channel TFT are left, and a third resist mask is formed afterwards over a first area where one of the p-channel TFT and the n-channel TFT is to be formed; thus, a source region and a drain region are formed in a semiconductor film of the other one of the p-channel TFT and the n-channel TFT by adding first impurity ions using the second resist mask and the third resist mask. After that, the first resist mask, the second resist mask, and the third resist mask are removed, and a source region and a drain region are formed in a semiconductor film of the one of the p-channel TFT and the n-channel TFT by adding second impurity ions using a fourth resist mask.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique by which a thin filmtransistor (hereinafter referred to as a TFT), particularly, a p-channelTFT and an n-channel TFT are formed over a glass substrate or a filmsubstrate.

2. Description of the Related Art

Thin film transistors (hereinafter referred to as TFTs) are used for apixel area and a peripheral circuit in a liquid crystal display or an ELdisplay. Further, a circuit using a p-channel TFT and an n-channel TFT,for example, a CMOS circuit is used for the circuit.

A semiconductor device having such a configuration is manufacturedthrough, for example, manufacturing processes shown in FIGS. 27A to 27D(Reference 1: Japanese Patent Laid-Open No. 4-286367).

(1) an amorphous silicon (a-Si) film is deposited on an insulatingsubstrate 201, and crystallized afterwards to form a crystalline silicon(p-Si) film. The crystalline silicon (p-Si) film is etched to form asemiconductor layer of a p-channel TFT and a semiconductor layer 203 ofan n-channel TFT (FIG. 27A).

(2) a gate insulating film 204 is formed (FIG. 27A).

(3) a gate electrode 205 for a p-channel TFT and a gate electrode 205for an n-channel TFT are formed (FIG. 27B).

(4) a photoresist 211 is formed in a p-channel TFT area or an n-channelTFT area (FIG. 27B).

(5) an n-type impurity ion or p-type impurity ion 212 is added to form asource region 206 and a drain region 206 of an n-channel TFT or ap-channel TFT. At this time, due to a shield effect of the gateelectrode, impurity ions are not added into a channel region of the TFT(FIG. 27B).

(6) a photoresist 211 is formed in an n-channel TFT or p-channel TFTarea (FIG. 27C).

(7) a p-type impurity ion or n-type impurity ion 213 is added to form asource region 207 and a drain region 207 of a p-channel TFT or ann-channel TFT. At this time, due to a shield effect of the gateelectrode, an impurity ion is not added into a channel region of the TFT(FIG. 27C).

(8) an interlayer insulating film 208 is formed and a contact hole isformed after that. Source and drain electrodes 210 are formed in each ofa p-channel TFT region and an n-channel TFT region (FIG. 27D).

Generally, ions containing boron, ions containing phosphorus, or ionscontaining arsenic are used as the impurity ions. For the impurity ions,B₂H₆ (diborane) gas, PH₃ phosphine) gas, and AsH₃ (arsine) gas which arediluted with hydrogen gas are used respectively, and the impurity ionsare added by an ion shower doping method. An “ion shower doping method”is one in which irradiation with ions having kinetic energy is performedto add impurity ions. Unlike the case of using a conventional ionimplanter, ions extracted from an ion source are used as is, without theuse of ion mass separation. In this method, besides desired n-type orp-type impurity ions, hydrogen ions are also added into a semiconductorfilm.

In the case where a TFT is miniaturized or a metal material or the likeused for a gate electrode is reduced in order to reduce cost, it isnecessary to make the gate electrode into a thin film. However, if thegate electrode is a thin film, there is a problem in that hydrogen ionsin a diluent gas penetrate into a channel region when a source regionand a drain region are formed by adding impurity ions. Therefore,degradation of TFT characteristics is a concern.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention tomanufacture a TFT with less degradation of the characteristics when ap-channel TFT and an n-channel TFT are manufactured over one substrate.

In the invention, a first resist mask and a second resist mask used forforming a gate electrode for a p-channel TFT and a gate electrode for ann-channel TFT are left, and a third resist mask is formed afterwardsover a first area where one of the p-channel TFT and the n-channel TFTis to be formed; thus, a source region and a drain region are formed ina first semiconductor film of the other one of the p-channel TFT and then-channel TFT by adding first impurity ions using the second resist maskand the third resist mask.

Further, after that, the first resist mask, the second resist mask, andthe third resist mask are removed, and after a fourth resist mask isformed over a second area where the other one of p-channel TFT and then-channel TFT is to be formed, a source region and a drain region areformed in a second semiconductor film of the one of the p-channel TFTand the n-channel TFT by adding second impurity ions using the fourthresist mask.

Alternatively, after the first resist mask, the second resist mask, andthe third resist mask are removed, a fourth resist mask and a fifthresist mask are formed over the gate electrode for the p-channel TFT andthe gate electrode for the n-channel TFT. After forming a sixth resistmask over the second area where the other one of the p-channel TFT andthe n-channel TFT is to be formed, second impurity ions are added usingthe sixth resist mask; thus a source region and a drain region may beformed in a second semiconductor film of the one of the p-channel TFTand the n-channel TFT.

Ions containing boron are used for p-type impurity ions, and ionscontaining phosphorus or ions containing arsenic are used for n-typeimpurity ions and they are added into the semiconductor film by an ionshower doping method. The ions containing boron are generated from B₂H₆(diborane) gas diluted with H₂ (hydrogen) gas, and ions containingphosphorus or ions containing arsenic are generated from PH₃ (phosphine)gas diluted with H₂ (hydrogen) gas or AsH₃ (arsine) gas diluted with H₂(hydrogen) gas. At this time, hydrogen ions are generated in addition toimpurity ions. However, in the above configuration, hydrogen can beprevented from penetrating into the channel region of the TFT whenadding the first impurity ions.

Alternatively, a fourth resist mask and a fifth resist mask may beformed over the gate electrode, and a sixth resist mask may be formedover the other one of the areas where the TFTs are formed, therebypreventing hydrogen from penetrating into the channel region of the TFTwhen adding the second impurity ions.

At this time, accelerating voltage or acceleration energy of the secondimpurity ions may be lower than accelerating voltage or accelerationenergy of the first impurity ions. When accelerating voltage oracceleration energy of the impurity ions is reduced, the acceleratingvoltage or the acceleration energy of hydrogen ions is reduced.Accordingly, even in the case where the fourth resist mask or the fifthresist mask is not formed over the gate electrode, hydrogen can beprevented from penetrating into the channel region.

The present invention includes the steps of forming a semiconductorfilm; forming a first semiconductor film and a second semiconductor filmby processing the semiconductor film; forming a gate insulating filmover the first semiconductor film and the second semiconductor film;forming a conductive film over the gate insulating film; forming a firstresist mask and a second resist mask over the conductive film; forming afirst gate electrode over the first semiconductor film with the gateinsulating film therebetween by processing the conductive film using thefirst resist mask, while forming a second gate electrode over the secondsemiconductor film with the gate insulating film therebetween byprocessing the conductive film using the second resist mask; forming athird resist mask so as to cover the first semiconductor film, the firstgate electrode, and the first resist mask in a state where the firstresist mask and the second resist mask remain; adding p-type impurityions into the second semiconductor film by an ion shower doping methodusing the second resist mask and the third resist mask, thereby forminga source region and a drain region; removing the first resist mask, thesecond resist mask, and the third resist mask; forming a fourth resistmask so as to cover the second semiconductor film and the second gateelectrode; and adding n-type impurity ions into the first semiconductorfilm by an ion shower doping method using the fourth resist mask,thereby forming a source region and a drain region, wherein the p-typeimpurity ions are formed of B₂H₆ (diborane) gas diluted with H₂(hydrogen) gas, and the n-type impurity ions are formed of PH₃(phosphine) gas diluted with H₂ (hydrogen) gas or AsH₃ (arsine) gasdiluted with H₂ (hydrogen) gas.

Alternatively, the invention includes the steps of forming asemiconductor film over a substrate; forming a first semiconductor filmand a second semiconductor film by processing the semiconductor film;forming a gate insulating film over the first semiconductor film and thesecond semiconductor film; forming a conductive film over the gateinsulating film; forming a first resist mask and a second resist maskover the conductive film; forming a first gate electrode over the firstsemiconductor film with the gate insulating film therebetween byprocessing the conductive film using the first resist mask, whileforming a second gate electrode over the second semiconductor film withthe gate insulating film therebetween by processing the conductive filmusing the second resist mask; forming a third resist mask so as to coverthe first semiconductor film, the first gate electrode, and the firstresist mask in a state where the first resist mask and the second resistmask remain; adding n-type impurity ions into the second semiconductorfilm by an ion shower doping method using the second resist mask and thethird resist mask, thereby forming a source region and a drain region;removing the first resist mask, the second resist mask, and the thirdresist mask; forming a fourth resist mask so as to cover the secondsemiconductor film and the second gate electrode; and adding p-typeimpurity ions into the first semiconductor film by an ion shower dopingmethod using the fourth resist mask, thereby forming a source region anda drain region, wherein the p-type impurity ions are formed of B₂H₆(diborane) gas diluted with H₂ (hydrogen) gas, and the n-type impurityions are formed of PH₃ phosphine) gas diluted with H₂ (hydrogen) gas orAsH₃ (arsine) gas diluted with H₂ (hydrogen) gas.

Further, in the above process, thickness of the gate insulating film maybe 10 nm to 200 nm, thickness of the gate electrode may be 100 nm to 500nm, and thickness of the first resist mask, the second resist mask, thethird resist mask, and the fourth resist mask may be 1.0 μm to 1.5 μm.

Further, the gate insulating film may be a silicon oxide film and thegate electrode may be formed from a TaN film and a W film over the TaNfilm. Further, the thickness of the gate electrode may be thinner than400 nm.

The invention includes the steps of forming a semiconductor film over asubstrate; forming a first semiconductor film and a second semiconductorfilm by processing the semiconductor film; forming a gate insulatingfilm over the first semiconductor film and the second semiconductorfilm; forming a conductive film over the gate insulating film; forming afirst resist mask and a second resist mask over the conductive film;forming a first gate electrode over the first semiconductor film withthe gate insulating film therebetween by processing the conductive filmusing the first resist mask, while forming a second gate electrode overthe second semiconductor film with the gate insulating film therebetweenby processing the conductive film using the second resist mask; forminga third resist mask so as to cover the first semiconductor film, thefirst gate electrode, and the first resist mask in a state where thefirst resist mask and the second resist mask remain; adding p-typeimpurity ions into the second semiconductor film by an ion shower dopingmethod using the second resist mask and the third resist mask, therebyforming a source region and a drain region; removing the first resistmask, the second resist mask, and the third resist mask; forming afourth resist mask over the first gate electrode while forming a fifthresist mask over the second gate electrode; forming a sixth resist maskso as to cover the second semiconductor film, the second gate electrode,and the fifth resist mask; and adding n-type impurity ions into thesecond semiconductor film by an ion shower doping method using thefourth resist mask and the sixth resist mask, wherein the p-typeimpurity ions are formed of B₂H₆ (diborane) gas diluted with H₂(hydrogen) gas, and the n-type impurity ions are formed of PH₃(phosphine) gas diluted with H₂ (hydrogen) gas or AsH₃ (arsine) gasdiluted with H₂ (hydrogen) gas.

The invention includes the steps of forming a semiconductor film over asubstrate; forming a first semiconductor film and a second semiconductorfilm by processing the semiconductor film; forming a gate insulatingfilm over the first semiconductor film and the second semiconductorfilm; forming a conductive film over the gate insulating film; forming afirst resist mask and a second resist mask over the conductive film;forming a first gate electrode over the first semiconductor film withthe gate insulating film therebetween by processing the conductive filmusing the first resist mask, while forming a second gate electrode overthe second semiconductor film with the gate insulating film therebetweenby processing the conductive film using the second resist mask; forminga third resist mask so as to cover the first semiconductor film, thefirst gate electrode, and the first resist mask in a state where thefirst resist mask and the second resist mask remain; adding n-typeimpurity ions into the second semiconductor film by an ion shower dopingmethod using the second resist mask and the third resist mask, therebyforming a source region and a drain region; removing the first resistmask, the second resist mask, and the third resist mask; forming afourth resist mask over the first gate electrode while forming a fifthresist mask over the second gate electrode; forming a sixth resist maskso as to cover the second semiconductor film, the second gate electrode,and the fifth resist mask; and adding p-type impurity ions into thesecond semiconductor film by an ion shower doping method using thefourth resist mask and the sixth resist mask, thereby forming a sourceregion and a drain region, wherein the p-type impurity ions are formedof B₂H₆ (diborane) gas diluted with H₂ (hydrogen) gas, and the n-typeimpurity ions are formed of PH₃ (phosphine) gas diluted with H₂(hydrogen) gas or AsH₃ (arsine) gas diluted with H₂ (hydrogen) gas.

Further, the thickness of the gate insulating film may be 10 nm to 200nm, the thickness of the gate electrode may be 100 nm to 500 μm, andthickness of the first resist mask, the second resist mask, the thirdresist mask, the fourth resist mask, the fifth resist mask, and thesixth may be 1.0 μm to 1.5 μm.

Further, the gate insulating film may be a silicon oxide film and thegate electrode may be formed from a TaN film and a W film over the TaNfilm. The thickness of the gate electrode may be thinner than 400 nm.

Considering accelerating voltage or accelerating energy of hydrogen ionsgenerated simultaneously with the impurity ions, in the case where then-type impurity ions are added after adding the p-type impurity ions,the accelerating voltage or accelerating energy of the n-type impurityions may be lower than the accelerating voltage or accelerating energyof the p-type impurity ions. Thus, the accelerating voltage oraccelerating energy of hydrogen ions generated simultaneously with then-type impurity ions can be made lower than that of hydrogen ionsgenerated simultaneously with the p-type impurity ions.

The accelerating voltage of the p-type impurity ions may be 50 kV to 100kV, and the accelerating voltage of the n-type impurity ions may be 30kV to 80 kV.

Further, the dose of the p-type impurity ions may be less than the doseof the n-type impurity ions. Thus, hydrogen ions generatedsimultaneously with the n-type impurity ions can be made less thanhydrogen ions generated simultaneously with the p-type impurity ions.

The concentration of p-type impurities in the second semiconductor filmmay be 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³, and concentration of the n-typeimpurities of the first semiconductor film may be 1.0×10¹⁹ cm⁻³ to1.0×10²¹ cm⁻³.

In the case where the p-type impurity ions are added after adding then-type impurity ions, the accelerating voltage or accelerating energy ofthe p-type impurity ions may be lower than the accelerating voltage oraccelerating energy of the n-type impurity ions.

Further, accelerating voltage of the n-type impurity ions may be 50 kVto 100 kV, and accelerating voltage of the p-type impurity ions may be30 kV to 80 kV.

Further, the dose of the n-type impurity ions may be less than the doseof the p-type impurity ions. Thus, hydrogen ions generatedsimultaneously with the p-type impurity ions can be made less thanhydrogen ions generated simultaneously with the n-type impurity ions

Further, the concentration of n-type impurities in the firstsemiconductor film may be 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³ or less, andconcentration of the p-type impurities of the second semiconductor filmmay be 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³.

In accordance with the present invention, the problem of hydrogen ionsthat are generated in addition to impurity ions penetrating into achannel region is alleviated. Furthermore, the gate electrode can bemade to be a thin film; thus, cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1D are figures illustrating manufacturing steps of asemiconductor device according to the present invention;

FIGS. 2A to 2D are figures illustrating manufacturing steps of asemiconductor device according to the present invention;

FIGS. 3A to 3C are figures illustrating manufacturing steps of asemiconductor device according to the present invention;

FIGS. 4A to 4E are figures illustrating manufacturing steps of asemiconductor device according to the present invention;

FIGS. 5A to 5E are figures illustrating manufacturing steps of asemiconductor device according to the present invention;

FIGS. 6A to 6D are figures illustrating manufacturing steps of asemiconductor device according to the present invention;

FIGS. 7A and 7B are figures illustrating manufacturing steps of asemiconductor device according to the present invention;

FIGS. 8A and 8B are figures illustrating manufacturing steps of an IDchip;

FIGS. 9A and 9B are figures illustrating manufacturing steps of an IDchip;

FIGS. 10A and 10B are figures illustrating manufacturing steps of an IDchip;

FIG. 11 is a figure illustrating a manufacturing step of an ID chip;

FIGS. 12A to 12C are figures showing application examples of ID chips;

FIGS. 13A to 13H are figures showing application examples of ID chips;

FIG. 14 is a figure showing a manufacturing step of a liquid crystaldisplay device;

FIG. 15 is a figure showing a manufacturing step of a liquid crystaldisplay device;

FIG. 16 is a top view of a pixel area of a liquid crystal displaydevice;

FIGS. 17A to 17D are figures illustrating manufacturing steps of aliquid crystal display device;

FIGS. 18A and 18B are figures illustrating manufacturing steps of aliquid crystal display device;

FIGS. 19A to 19D are figures illustrating manufacturing steps of an ELdisplay device;

FIGS. 20A to 20C are figures illustrating manufacturing steps of an ELdisplay device;

FIGS. 21A and 21B are figures illustrating manufacturing steps of an ELdisplay device;

FIGS. 22A and 22B are cross-sectional views of an EL display device;

FIGS. 23A to 23F are equivalent circuit diagrams of an EL displaydevice;

FIG. 24 is an equivalent circuit diagram of an EL display device;

FIGS. 25A to 25E are figures showing examples of electronic device towhich the present invention is applied;

FIG. 26 is a figure showing an example of an electronic device to whichthe present invention is applied;

FIGS. 27A to 27D are figures illustrating a related art;

FIGS. 28A and 28B are graphs showing drain current—gate voltagecharacteristics and mobility—gate voltage characteristics of a p-channelTFT of an embodiment;

FIG. 29 is a chart showing ON-state current characteristics of ap-channel TFT of an embodiment and a comparative example;

FIG. 30 is a chart showing mobility characteristics of a p-channel TFTof an embodiment and a comparative example;

FIG. 31 is a chart showing threshold characteristics of an embodimentand a comparative example;

FIGS. 32A and 32B are graphs showing drain current—gate voltagecharacteristics and mobility—gate voltage characteristics of ann-channel TFT of an embodiment.

FIG. 33 is a chart showing ON-state current characteristics of ann-channel TFT of an embodiment and a comparative example;

FIG. 34 is a chart showing mobility characteristics of a n-channel TFTof an embodiment and a comparative example;

FIG. 35 is a chart showing threshold characteristics of an n-channel TFTof an embodiment and a comparative example.

DETAILED DESCRIPTION OF THE INVENTION

Preferred Embodiment Modes and Embodiment of the present invention willbe described with reference to the drawings. Note that the presentinvention can be embodied with many different modes, and it is easilyunderstood by those skilled in the art that the mode and detail can bevariously modified without departing from the sprit and scope of thepresent invention. Therefore, the present invention is not construed asbeing limited to the description of Embodiment Modes and Embodiment.

Embodiment Mode 1

Here, a method will be described, in which a first resist mask and asecond resist mask which are used in forming a gate electrode for ap-channel TFT and a gate electrode for an n-channel TFT are left; aftera third resist mask is formed over a first area where one of thep-channel TFT and the n-channel TFT is to be formed, first impurity ionsare added using a second resist mask and third resist mask to form asource region and a drain region in a semiconductor film of the otherone of the p-channel TFT and the n-channel TFT; after that, the firstresist mask, the second resist mask, and the third resist mask areremoved; and after a fourth resist mask is formed over a second areawhere the other one of the p-channel TFT and the n-channel TFT is to beformed, second impurity ions are added using a gate electrode and afourth resist mask to form a source region and a drain region in asemiconductor film of the one of the p-channel TFT and the n-channelTFT.

First, as shown in FIG. 1A, a semiconductor film 40 is formed to athickness of 10 nm to 200 nm over a substrate 1.

As the substrate 1, a glass substrate, a quartz substrate, a substrateformed of an insulating material such as alumina, a plastic substratewhich is heat-resistant to the processing temperature of a subsequentstep, a silicon wafer, a metal substrate, or the like can be used.

In the case of using a plastic substrate for the substrate 1, PC(polycarbonate), PES (polyethylene sulfone), PET (polyethyleneterephthalate), PEN polyethylene naphthalate), or the like which haverelatively high glass transition temperature is preferably used.

An insulating film 2 may be formed over the substrate surface. Siliconoxide (SiO_(x)), silicon nitride (SiN_(x)), silicon oxynitride(SiO_(x)N_(y)) (x>y), silicon nitride oxide (SiN_(x)O_(y)) (x>y), or thelike may be used for the insulating film 2. The insulating film 2 canprevent diffusion of impurities or the like from the substrate side. Theinsulating film 2 may have a thickness of 10 nm to 200 nm.Alternatively, a substrate in which an insulating film of a siliconoxide, silicon nitride, or the like is formed on a surface of asubstrate of metal such as stainless-steel or a semiconductor substratemay be used.

The insulating film 2 may be formed by treating the surface of thesubstrate 1 with high-density plasma. The high-density plasma isgenerated by using, for example, a microwave of 2.45 GHz, and is assumedto have an electron density of 1×10¹¹/cm³ to 1×10¹³/cm³, an electrontemperature of 2 eV or less, and an ion energy of 5 eV or less. Activespecies of such high-density plasma has low kinetic energy, and damagedue to plasma is less than the case of a conventional plasma treatment;thus, a film with few defects can be formed. The distance from anantenna generating a microwave to the substrate 1 is preferably set tobe 20 mm to 80 mm, more preferably, 20 mm to 60 mm.

In addition, the surface of the substrate 1 can be nitrided byperforming the above-described high-density plasma treatment in anitriding atmosphere, for example, in an atmosphere including nitrogenand a rare gas, an atmosphere including nitrogen, hydrogen, and a raregas, or an atmosphere including ammonia and a rare gas. In the case ofusing a glass substrate, a quartz substrate, a silicon wafer, or thelike as the substrate 1 and performing nitriding treatment with theabove-described high-density plasma, a nitride film formed on thesurface of the substrate 1 contains silicon nitride as its maincomponent; thus, the nitride film can be used as the insulating film 2.A silicon oxide film or a silicon oxynitride film may be formed over thenitride film by plasma CVD, which may be used as the insulating film 2including a plurality of layers.

In addition, a nitride film can be formed on the surface of theinsulating film 2 formed of silicon oxide, silicon oxynitride, or thelike by similarly performing nitriding treatment with high-densityplasma on the surface of the insulating film 2. This nitride film cansuppress diffusion of impurities from the substrate 1. In addition, thenitride film can be formed to be very thin. Therefore, influence ofstress upon the semiconductor layer to be formed thereover can bereduced.

The semiconductor film 40 is formed using silicon, silicon-germanium,silicon-germanium-carbon, or the like. As a method for forming thesemiconductor film 40, known CVD, sputtering, coating, vapor deposition,or the like can be used. The semiconductor film 40 may be any one of anamorphous semiconductor film, a crystalline semiconductor film, or asingle crystalline semiconductor film.

In the case of using a crystalline semiconductor film, the following canbe used as the formation method: a method of directly forming acrystalline semiconductor film, or a method of forming an amorphoussemiconductor film over the substrate 1 and then crystallizing it.

As a method of crystallizing an amorphous semiconductor film, thefollowing can be used as the method: a method of crystallizing anamorphous semiconductor film by irradiation with a laser beam 41 (FIG.4A); a method of crystallizing an amorphous semiconductor film byheating using an element which promotes the crystallization of thesemiconductor film; or a method of crystallizing an amorphoussemiconductor film by heating using an element which promotes thecrystallization of the semiconductor film and then irradiating thesemiconductor film with a laser beam (FIGS. 4B and 4C). Naturally, amethod of thermally crystallizing an amorphous semiconductor filmwithout using the element can be used as well. However, such the methodcan be applied only in the case where the substrate is a quartzsubstrate, a silicon wafer, or the like which can withstand the hightemperature.

In the case of laser irradiation, a continuous wave laser beam (CW laserbeam) or a pulsed laser beam can be used. Here, a beam emitted from oneor plural kinds of a gas laser such as an Ar laser, a Kr laser, or anexcimer laser; a laser using, as a medium, single crystalline YAG, YVO₄,forsterite (Mg₂SiO₄), YAlO₃, or GdVO₄ or polycrystalline (ceramic) YAG,Y₂O₃, YVO₄, YAlO₃, or GdVO₄ doped with one or more of Nd, Yb, Cr, Ti,Ho, Er, Tm, and Ta as a dopant; a glass laser; a ruby laser; analexandrite laser; a Ti: sapphire laser; a copper vapor laser; and agold vapor laser, can be used as the laser beam. By irradiation with alaser beam having a fundamental wave of such lasers or one of the secondto fourth harmonics, a crystal with a large grain size can be obtained.For example, the second harmonic (532 nm) or the third harmonic (355 nm)of an Nd:YVO₄ laser (fundamental wave of 1,064 nm) can be used. In thiscase, the power density of about 0.01 MW/cm² to 100 MW/cm² (preferably,0.1 MW/cm² to 10 MW/cm²) is required for the laser. The scanning rate isapproximately set at about 10 cm/sec to 2,000 cm/sec to irradiate thesemiconductor film.

Note that each laser using, as a medium, single crystalline YAG, YVO₄,forsterite (Mg₂SiO₄), YAlO₃, or GdVO₄ or polycrystalline (ceramic) YAG,Y₂O₃, YVO₄, YAlO₃, or GdVO₄ doped with one or more of Nd, Yb, Cr, Ti,Ho, Er, Tm, and Ta as a dopant; an Ar ion laser; and a Ti: sapphirelaser, is capable of continuous oscillation. Further, pulse oscillationthereof can be performed at a repetition rate of 10 MHz or more bycarrying out Q switch operation or mode synchronization. When a laserbeam is emitted at a repetition rate of 10 MHz or more, a semiconductorfilm is irradiated with a next pulse while the semiconductor film ismelted by the laser beam and then solidified. Therefore, unlike the caseof using a pulsed laser with a low repetition rate, a solid-liquidinterface can be continuously moved in the semiconductor film so thatcrystal grains, which continuously grow in a scanning direction, can beobtained.

When ceramic (polycrystal) is used as a medium, the medium can be formedto have a free shape for a short time at low cost. When using a singlecrystal, a columnar medium with several mm in diameter and several tensof mm in length is usually used. In the case of using the ceramic, amedium bigger than the case of using the single crystal can be formed.

A concentration of a dopant such as Nd or Yb in a medium, which directlycontributes to light emission, cannot be changed largely in either caseof the single crystal or the polycrystal; therefore, there is somelimitation on improvement in output of a laser by increasing theconcentration of the dopant. However, in the case of a ceramic, the sizeof a medium can be significantly increased as compared with the case ofthe single crystal; thus, drastic improvement in output of a laser canbe expected.

Further, in the case of a ceramic, a medium with a parallelepiped shapeor a rectangular parallelepiped shape can be formed easily. In a case ofusing a medium having such a shape, when oscillated light is made travelin a zigzag manner inside the medium, a path of the oscillated light canbe made long. Therefore, amplification is increased and a laser beam canbe oscillated at high output. Furthermore, a cross section of a laserbeam emitted from a medium having such a shape has a quadrangular shape,which is advantageous when the laser beam is shaped into a quadrangularshape in cross section as compared with a laser beam with a circularshape. By shaping a laser beam emitted in the above described mannerusing an optical system, a linear beam having a length of 1 mm or lesson a shorter side and a length of several mm to several m on a longerside can be easily obtained. In addition, when a medium is uniformlyirradiated with excited light, energy distribution of a linear beam isuniform in a longer side direction.

When a semiconductor film is irradiated with this linear beam, the wholesurface of the semiconductor film can be annealed more uniformly. In acase where uniform annealing is required from one end to the other endof the linear beam, for example, an arrangement in which slits areprovided in either end of the linear beam is required thereby shieldinglight at a portion where energy is attenuated.

When a semiconductor film is annealed using the thus obtained linearbeam having uniform intensity and an electronic device is manufacturedby using this semiconductor film, characteristics of the electronicdevice are good and uniform.

As the method of crystallizing the semiconductor film by heating with anelement which promotes the crystallization of the semiconductor film, atechnique disclosed in Japanese Patent Laid-Open No. 8-78329, the entirecontents of which are hereby incorporated by reference, can be used. Asto the technique in the patent application publication, an amorphoussemiconductor film is doped with a metal element 42 which promotes thecrystallization of the semiconductor film, and then heat treatment iscarried out so that the amorphous semiconductor film is crystallizedwith the doped region as a nucleus (FIG. 4B).

An amorphous semiconductor film can also be crystallized by performingirradiation with strong light instead of the heat treatment. In thatcase, any one of or a combination of infrared light, visible light, andultraviolet light can be used. Typically, light emitted from a halogenlamp, a metal halide lamp, a xenon arc lamp, a carbon arc lamp, a highpressure sodium lamp, or a high pressure mercury lamp is used. The lamplight source is lighted for 1 to 60 seconds, or preferably 30 to 60seconds, and such lighting is repeated 1 to 10 times, or preferably 2 to6 times. The light-emission intensity of the lamp light source isarbitrary, but the semiconductor film is instantaneously heated up to600° C. to about 1000° C. Note that if necessary, heat treatment may beperformed in order to discharge the hydrogen contained in the amorphoussemiconductor film 40 having an amorphous structure before theirradiation with the strong light. Alternatively, crystallization may beperformed by both the heat treatment and irradiation with strong light.

After the heat treatment, in order to increase the crystallization rateof the crystalline semiconductor film (rate of area occupied bycrystalline components against the whole volume of the film) and tocorrect defects which remain in the crystalline grains, the crystallinesemiconductor film may be irradiated with the laser beam 41 in theatmospheric air or an oxygen atmosphere. The laser beam may be selectedfrom the aforementioned ones (FIG. 4C).

Further, the metal element contained in the crystalline semiconductorfilm is required to be removed. The method will be described below.

First, the surface of the crystalline semiconductor film is treated witha solution containing ozone (typically, ozone water), thereby forming abarrier layer 43 formed from an oxide film (called chemical oxide) onthe surface of the crystalline semiconductor film to a thickness of 1 nmto 10 nm (FIG. 40). The barrier layer 43 functions as an etching stopperwhen only a gettering layer is selectively removed in a subsequent step.

Then, a gettering layer containing a rare gas element is formed as agettering site over the barrier layer 43. Here, a semiconductor filmcontaining a rare gas element is formed as the gettering layer 44 by CVDor sputtering (FIG. 4D). When forming the gettering layer, thesputtering conditions are controlled as appropriate so that a rare gaselement is added thereto. The rare gas element may be one or more ofhelium (He), neon (Ne), argon (Ar), krypton (Kr), or xenon (Xe).

Note that in the case of forming the gettering layer by using a feed gascontaining phosphorus which is an impurity element having oneconductivity type or using a target including phosphorus, gettering canbe performed by utilizing the coulomb force of phosphorus in addition tothe gettering using the rare gas element. In gettering, a metal element(e.g., nickel) tends to move to a region having a high concentration ofoxygen; therefore, the concentration of oxygen contained in thegettering layer 43 is desirably set at 5×10¹⁸/cm³ or higher, forexample.

Next, the crystalline semiconductor film, the barrier layer and thegettering layer is subjected to thermal treatment (e.g., heat treatmentor irradiation with strong light), thereby the metal element (e.g.,nickel) is gettered as shown by the arrows in FIG. 41) so that the metalelement in the crystalline semiconductor film is lowered inconcentration or removed.

Then, a known etching method is performed using the barrier layer 43 asan etching stopper, thereby only the gettering layer 44 is selectivelyremoved. After that, the barrier layer 43 formed from an oxide film isremoved, for example, using an etchant containing hydrofluoric acid(FIG. 4E).

Here, impurity ions may be added in consideration of thresholdcharacteristics of a TFT to be manufactured.

Next, a semiconductor film is formed into island-shaped semiconductorfilms 3 and 4 by a known photolithography process (FIG. 1B). Here, ap-channel TFT is formed using the semiconductor film 3, and an n-channelTFT is formed using the semiconductor film 4.

Then, after cleaning the surfaces of the semiconductor films with anetchant containing hydrofluoric acid, a gate insulating film 5 is formedto a thickness of 10 nm to 200 nm over the semiconductor films (FIG.1C). The surface cleaning and the formation of the gate insulating film5 may be continuously carried out without exposure to the atmosphere.The gate insulating film 5 is formed from an insulating film containingsilicon as a main component, for example, a silicon oxide film, asilicon nitride film, a silicon oxynitride film, a silicon nitride oxidefilm, or the like. Further, the gate insulating film may a single layeror a layered film.

Next, after cleaning the surface of the gate insulating film 5, aconductive film 6 forming a gate electrode is formed to a thickness of100 nm to 500 nm over the whole surface including the surface of thegate insulating film 5 (FIG. 1C). The conductive film 6 may be formed ofan element selected from tantalum (Ta), tungsten (W), titanium (Ti),molybdenum (Mo), or aluminum (Al); or an alloy material or a compoundmaterial containing one of the above elements as a main component.Alternatively, a semiconductor film typified by a polycrystallinesilicon film doped with an impurity element such as phosphorus (P) orthe like may be used. Further, the conductive film 6 may have a singlelayer structure or a layered structure including two or more layers.

The surface of the conductive film 6 is coated with a photoresist film,and this photoresist film is exposed and developed, thereby forming afirst resist mask 7 a and a second resist mask 7 b to a thickness of 1.0μm to 1.5 μm. The conductive film 6 is etched using the resist masks 7 aand 7 b, thereby forming gate electrodes 8 a and 8 b over the gateinsulating film 5 (FIG. 1D). Here, the first resist mask 7 a and thesecond resist mask 7 b are not removed, and are used in the next dopingprocess. Note that the resist masks of this embodiment mode can beformed of a positive type resist containing novolac resin and anaphthoquinone diazide compound.

Further, a wire such as a gate wire can be formed from the same materialas the gate electrodes 8 a and 8 b. Here, the gate electrode or the wireis preferably led so as to have a round corner when seen from adirection perpendicular to the substrate 1. By making the corners round,dust or the like can be prevented from remaining at the corners of thewire; thus, the number of defects generated due to dust can be reducedand yield can be improved.

Next, coating with a photoresist film is carried out, and thephotoresist film is exposed and developed, thereby forming a thirdresist mask 9 to a thickness of 1.0 μm to 1.5 μm covering thesemiconductor film 4, the gate electrode 8 b, and the second resist mask7 b (FIG. 2A).

The semiconductor film 3 is doped with p-type impurity ions 10 (ionscontaining B) using the first resist mask 7 a, the second resist mask 7b, the third resist mask 9, and the gate electrodes 8 a and 8 b asmasks, thereby forming the source region 11 and the drain region 12. Thep-type impurity ions accelerate at 50 kV to 100 kV, and concentration ofthe p-type impurity is 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³. The p-typeimpurity ions are added to the semiconductor film by an ion showerdoping method using diborane (B₂H₆) gas diluted with hydrogen gas. Atthis time, not only ions containing B but also hydrogen ions aregenerated. The gate electrode serves as a mask when the ions containingB are added; however, hydrogen ions easily penetrate through the gateelectrode and penetrate the channel region of the semiconductor layerthereunder.

However, in the present invention, since the gate insulating film 5, thethird resist mask 9, the second resist mask 7 b, and the gate electrode8 b are formed over the area under the gate electrode of thesemiconductor film 4, that is, a channel region 22, it is extremelyunlikely that hydrogen ions will penetrate it.

Meanwhile, although the third resist mask 9 is not formed over a channelregion 21 of the semiconductor film 3, the gate insulating film 5, thegate electrode 8 a, and the first resist mask 7 a are formed thereover,so it is unlikely that hydrogen ions will penetrate it. This effect issignificant when the thickness of the gate electrode is thinner than 400nm.

Next, the third resist mask 9, the first resist mask 7 a, and the secondresist mask 7 b are removed by a method such as ashing (FIG. 2B).

Then, coating with a photoresist film is carried out, and thephotoresist film is exposed and developed, so that a fourth resist mask13 is formed to a thickness of 1.0 μm to 1.5 μm covering thesemiconductor film 3, and the gate electrode 8 a (FIG. 2C).

The n-type impurity ions 14 (ions containing phosphorus, ions containingarsenic, or the like) are introduced into the semiconductor film 4 usingthe fourth resist mask 13, the gate electrodes 8 a and 8 b as masks,thereby forming a source region 15 and a drain region 16 (FIG. 2C). Then-type impurity ions accelerates at 30 kV to 80 kV, and concentration ofthe n-type impurity is 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³. For example, thesemiconductor film 4 is doped with the n-type impurity ions by a showerdoping method using phosphine (PH₃) gas diluted with hydrogen gas.

At this time, the accelerating voltage or acceleration energy of then-type impurity ions is preferably lower than the accelerating voltageor acceleration energy of the p-type impurity ions. When theaccelerating voltage or acceleration energy of the p-type impurity ionsis decreased, the accelerating voltage or acceleration energy of thehydrogen ions generated concurrently with the impurity ions is alsodecreased. Therefore, even if a resist mask is not formed over gateelectrodes 8 a and 8 b, the number of hydrogen ions penetrating thechannel regions 21 and 22 can be reduced.

The dose of the n-type impurity ions is preferably less than the dose ofthe p-type impurity ions. Thus, the dose of hydrogen ions generatedconcurrently with the n-type impurity ions can be made less than that ofhydrogen ions generated concurrently with the p-type impurity ions;therefore, even when hydrogen ions penetrate the channel regions,deterioration can be prevented.

Here, heat treatment, irradiation with laser light or intense light, RTAor the like may be performed to activate the source regions and thedrain regions.

Thus the semiconductor film 3 becomes a p-channel TFT, and thesemiconductor film 4 becomes an n-channel TFT.

Here, p-type impurity ions are added first and n-type impurity ions areadded afterwards; however, the order may be reversed. In that case, theaccelerating voltage or acceleration energy of the p-type impurity ionsis preferably lower than the accelerating voltage or acceleration energyof the n-type impurity ions. As the accelerating voltage, the voltagedescribed above can be used. Therefore, even if a resist mask is notformed over the gate electrodes 8 a and 8 b, the number of hydrogen ionspenetrating the channel regions can be reduced.

Further, the dose of p-type impurity ions is preferably less than thedose of the n-type impurity ions. Thus, the dose of hydrogen ionsgenerated simultaneously with p-type impurity ions can be made less thanthat of hydrogen ions generated simultaneously with the n-type impurityions. Further, even when hydrogen ions penetrate the channel regions,deterioration can be prevented.

Next, an interlayer insulating film 17 is formed over the whole surfaceincluding the surfaces of the gate insulating film 5 and the gateelectrodes 8 a and 8 b, and hydrogenation is carried out. As theinterlayer insulating film 17, a silicon nitride film, a silicon oxidefilm, a silicon oxynitride film, or a silicon nitride oxide film can beused.

Then, a resist mask is formed over the interlayer insulating film 17,and the interlayer insulating film 17 is etched using the resist mask;thus, contact holes located above each of the source regions 11 and 12and each of the drain regions 15 and 16 are formed.

After the resist mask is removed and a conductive film is formed,etching is carried out using another resist mask, thereby forming anelectrode or a wire 18 (a source wire and a drain wire of the TFTs, or acurrent supply wire of the TFTs) (FIG. 2D). Note that, in thisembodiment mode, the electrode and the wire are integrated; however, theelectrode and the wire may be separately formed and connectedelectrically. As the conductive film, a layered film of TiN, Al, andTiN, or an Al alloy film can be used.

Here, the electrode or the wire is preferably led so as to have a roundcorner when seen from a direction perpendicular to the substrate 1. Bymaking the corners round, dust or the like can be prevented fromremaining at the corners of the wire; thus, the number of defectsgenerated due to dust can be reduced and the yield can be improved.

A mask manufactured by exposure and development using a photosensitiveresist as a photomask is used for patterning. Transmittance of light forexposure in an arbitrary portion of the photomask is suppressed, therebycontrolling the thickness of the developed mask. By controlling thethickness of the mask, fine and accurate patterning can be performed.

A planarizing film to be a second interlayer insulating film 19 isformed. The planarizing film is formed using a light-transmittinginorganic material (silicon oxide, silicon nitride, silicon nitridecontaining oxygen, or the like), a photosensitive or non-photosensitiveorganic material (polyimide, acrylic, polyamide, polyimide amide, aresist, benzocyclobutene, or the like), or a stack thereof.Alternatively, the planarizing film may be formed using alight-transmitting film such as an insulating film formed from a SiO_(x)film containing an alkyl group obtained by a coating method. Forexample, an insulating film formed of silica glass, alkyl siloxanepolymers, alkylsilsesquioxane polymers, hydrogen silsesquioxanepolymers, hydrogen alkylsilsesquioxane polymers, or the like can beused. As examples of siloxane-based polymers, there are coatinginsulating film materials such as PSB-K1 and PSB-K31 product of Torayindustries, Inc.) and a coating insulating film material such as ZRS-5PH(product of Catalysts & Chemicals Industries Co., Ltd.).

Contact holes are formed in the second interlayer insulating film 19using another resist mask.

Next, a conductive film 20 is formed. The conductive film can be formedfrom a transparent conductive film using indium tin oxide containing aSi element, IZO (Indium Zinc Oxide) in which zinc oxide (ZnO) is mixedwith indium oxide, or the like other than indium tin oxide (ITO).

After that, the conductive film is patterned using another resist maskto form a electrode (FIG. 2D). Note that the conductive film is notrequired to be transparent if it is not used for a display device.

Embodiment Mode 2

Here, a method will be described in which a first resist mask and asecond resist mask used in forming a gate electrode for a p-channel TFTand a gate electrode for an n-channel TFT are left; a third resist isformed over a first area where one of the p-channel TFT and then-channel TFT is to be formed; first impurity ions are added afterwardsusing the second resist mask and the third resist mask, thereby forminga source region and a drain region in a semiconductor film of the otherone of the p-channel TFT and the n-channel TFT; after that, the firstresist mask, the second resist mask, and third resist mask are removed,and a fourth resist mask and a fifth resist mask are formed over thegate electrode for the p-channel TFT and the gate electrode for then-channel TFT; a sixth resist mask is formed over a second area wherethe other one of the p-channel TFT and the n-channel TFT is to beformed, and second impurity ions are added after that using the fourthresist mask, the fifth resist mask, and the sixth resist mask; thus, asource region and a drain region is formed in a semiconductor film ofthe one of the p-channel TFT and the n-channel TFT.

A material or a formation method of an insulating film, a semiconductorfilm, an electrode, a wire, a resist or the like can be the same as onesexplained in Embodiment Mode 1.

An insulating film 2 is formed; semiconductor films 3 and 4 are formed;a gate insulating film 5 is formed; gate electrodes 8 a and 8 b areformed using a first resist mask 7 a and a second resist mask 7 b; athird resist mask 9 is formed covering the semiconductor film 4, thegate electrode 8 b, and the second resist mask 7 b; the semiconductorfilm 3 is doped with p-type impurity ions 10 (ions containing B) usingthe first resist mask 7 a, the second resist mask 7 b, the third resistmask 9, and the gate electrodes 8 a and 8 b as masks, thereby formingthe source region 11 and the drain region 12; and the third resist mask9, the first resist mask 7 a, and the second resist mask 7 b are removedby ashing or the like. These steps are the same as those in EmbodimentMode 1 (FIGS. 1A to 1D, FIGS. 2A and 2B, FIGS. 4A to 4E).

Next, the surfaces of the gate electrodes 8 a and 8 b are coated with aphotoresist film and the photoresist film is exposed and developed,thereby forming a fourth resist mask 30 a and a fifth resist mask 30 bto a thickness of 1.0 μm to 1.5 μm over the gate electrodes 8 a and 8 b(FIG. 3A).

Subsequently, coating with a photoresist film is carried out and thephotoresist film is exposed and developed, thereby forming the sixthresist mask 31 to a thickness of 1.0 μm to 1.5 μm covering thesemiconductor film 3 and the gate electrode 8 a (FIG. 3B).

The n-type impurity ions 14 (ions containing phosphorus, ions containingarsenic, or the like) are introduced into the semiconductor film 4 usingthe sixth resist mask 31, the fifth resist mask 30 b, the gateelectrodes 8 a and 8 b as masks, thereby forming a source region 15 anda drain region 16 (FIG. 3B). The n-type impurity ions accelerate at 30kV to 80 kV. Further, concentration of the n-type impurity is 1.0×10¹⁹cm⁻³ to 1.0×10²¹ cm⁻³. For example, the semiconductor film 4 is dopedwith the n-type impurity ions by a shower doping method using phosphine(PH₃) gas diluted with hydrogen gas or arsine (AsH₃) gas diluted withhydrogen gas.

Here, since the gate insulating film, the sixth resist mask 31, thefourth resist mask 30 a, and the gate electrode 8 b are formed over theregion under the gate electrode of the semiconductor film 3, that is, achannel region 21; it is extremely unlikely that hydrogen ions willpenetrate the channel region 21.

Meanwhile, although the sixth resist mask 31 a is not formed over achannel region 22 of the semiconductor film 4, since the gate insulatingfilm, the gate electrode 8 a, and the fifth resist mask 30 b are formedover it, it is unlikely that hydrogen ions will penetrate the channelregion 22.

Further, if the accelerating voltage or acceleration energy of then-type impurity ions is made lower than the accelerating voltage oracceleration energy of the p-type impurity ions, the acceleratingvoltage or acceleration energy of the hydrogen ions can be decreased;thus, the number of hydrogen ions penetrating the channel region 22 canbe reduced even when the sixth resist mask 31 is not formed over thegate electrode 8 b.

The dose of the n-type impurity ions is preferably less than the dose ofthe p-type impurity ions. Thus, even when hydrogen ions penetrate thechannel regions, deterioration can be prevented.

Here, p-type impurity ions are added first and n-type impurity ions areadded afterwards; however, the order may be reversed.

The subsequent steps of forming an interlayer insulating film 17,forming a contact hole in the interlayer insulating film 17, forming anelectrode or wire 18 (a source wire and a drain wire of the TFT, acurrent supply wire of the TFT, or the like), forming a planarizing filmto be a second interlayer insulating film 19, forming a contact hole inthe second interlayer insulating film 19, and forming a conductive film20, are the same as those in Embodiment Mode 1 (FIG. 3C).

Embodiment Mode 3

Here, a method for manufacturing a semiconductor device which is capableof data transmission/reception without contact, for example, an IC tag,or an RFID using the present invention will be described. Note that,parts that are the same as those in the above embodiment modes aredenoted by the same reference numerals.

First, a release layer 100 is formed over one surface of the substrate 1(FIG. 8A). The substrate 1 is formed using a glass substrate, a quartzsubstrate, a metal substrate or a stainless substrate over one surfaceof which an insulating layer is formed, a plastic substrate which isresistant to the processing temperature of the present step, or thelike. There is no limitation on the size or the shape of a substratesuch as the substrate 1. When a substrate has a rectangular shape with alength of one meter or longer on a side, the productivity can bedrastically improved. Such an advantage is far superior to the casewhere a wireless chip is taken from a circular silicon substrate. Inaddition, a thin film integrated circuit formed over the substrate 1 isseparated from the substrate 1 later. In other words, the wireless chipprovided by the invention does not have the substrate 1. Accordingly,the substrate 1 from which a thin film integrated circuit is separatedcan be reused a number of times. In this manner, if the substrate 1 isreused, cost reduction can be achieved. The substrate 1 to be reused isdesirably a quartz substrate.

Note that in this embodiment, the release layer 100 is selectivelyprovided by forming a thin film over one surface of the substrate 1, andpatterning it by photolithography.

The release layer 100 is formed in a single layer or a stack by a knownmethod (e.g., sputtering or plasma CVD) using an element selected fromtungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), niobium(Nb), nickel (Ni), cobalt (Co), zirconium (Zr), zinc (Zr), ruthenium(Ru), rhodium (Rh), lead (Pd), osmium (Os), iridium (Ir), or silicon(Si), or an alloy material or compound material containing such elementsas a main component. A layer containing silicon may have any of anamorphous structure, a microcrystalline structure and a polycrystallinestructure.

If the release layer 100 has a single-layer structure, it is preferablyformed using a tungsten layer, a molybdenum layer, or a layer containinga mixture of tungsten and molybdenum. Alternatively, the release layer100 is formed using a layer containing tungsten oxide, layer containinga tungsten oxynitride, a layer containing molybdenum oxide, a layercontaining molybdenum oxynitride, or a layer containing oxide oroxynitride of a mixture of tungsten and molybdenum. Note that themixture of tungsten and molybdenum corresponds, for example, to an alloyof tungsten and molybdenum.

If the release layer 100 has a layered structure, preferably, a firstlayer thereof is formed of a tungsten layer, a molybdenum layer, or alayer containing a mixture of tungsten and molybdenum, and a secondlayer thereof is formed of oxide, nitride, oxynitride or nitride oxideof tungsten, molybdenum, or a mixture of tungsten and molybdenum.

In the case where the release layer 100 is formed with a layeredstructure of a layer containing tungsten and a layer containing tungstenoxide, the layer containing tungsten may be formed first and a siliconoxide layer may be formed thereon so that a tungsten oxide layer isformed at the interface between the tungsten layer and the silicon oxidelayer. This also applies to the case of forming a layer containingnitride, oxynitride or nitride oxide of tungsten. For example, afterforming a tungsten layer, a silicon nitride layer, a silicon oxynitridelayer, or a silicon nitride oxide layer is formed thereover. Note thatthe silicon oxide layer, the silicon oxynitride layer, the siliconnitride oxide layer or the like which is formed over the tungsten layerserves as a base insulating layer later.

The tungsten oxide is denoted by WO_(x), where x is 2 or 3. There arecases where x is 2 (the oxide is WO₂), x is 2.5 (the oxide is W₂O₅), xis 2.75 (the oxide is W₄O₁₁), x is 3 (the oxide is WO₃), and the like.In forming the oxide of tungsten, the x value is not specificallylimited to a certain value, and it may be determined based on theetching rate or the like. Note that a layer containing tungsten oxidewhich is formed by sputtering in an oxygen atmosphere has the bestetching rate (WO_(x), 0<x<3). Thus, in order to reduce manufacturingtime, the release layer is preferably formed using a layer containingtungsten oxide by sputtering in an oxygen atmosphere.

Note that the release layer 100 is formed so as to contact the substrate1 in the aforementioned step; however, the invention is not limitedthereto. For example, after forming an insulating layer to be a base soas to contact the substrate 1, the release layer 100 may be formed so asto contact the insulating layer.

Then, a base insulating layer 2 is formed to be a base so as to coverthe release layer 100. The insulating layer 2 is formed in a singlelayer or a stack by a known method (e.g., sputtering or plasma CVD)using a layer containing silicon oxide or a layer containing siliconnitride. Silicon oxide is a substance containing silicon (Si) and oxygen(O), which corresponds to silicon oxide, silicon oxynitride, siliconnitride oxide, or the like. The silicon nitride material is a substancecontaining silicon and nitrogen (N), which corresponds to siliconnitride, silicon oxynitride, silicon nitride oxide, or the like.

Then, after an amorphous silicon film is formed over the insulatinglayer 2, a p-channel TFT and an n-channel TFT are manufactured. The TFTscan be manufactured by using a method shown in the above embodimentmodes; therefore, the description is omitted here.

FIG. 8B shows one in which steps up to the formation of a TFT arefinished. As compared to FIG. 2D, difference is that a release layer isprovided under the insulating film over the substrate.

A conductive film 20 formed in the above embodiment mode functions as anantenna. Unlike the above embodiment mode, the conductive film 20 isformed in a single layer or a stack using an element selected fromaluminum (Al), titanium (Ti), silver (Ag), or copper (Cu) or an alloymaterial or a compound material containing such an element as a maincomponent. For example, the conductive film 20 may be formed by stackinga barrier layer, and an aluminum layer in this order, or a barrierlayer, an aluminum layer, and a barrier layer in this order. The barrierlayer corresponds to titanium, titanium nitride, molybdenum, molybdenumnitride, or the like.

Next, although not shown here, a protective layer may be formed by aknown method so as to cover the thin film integrated circuit 101. Theprotective layer corresponds to a layer containing carbon such as DLC(Diamond Like Carbon), a layer containing silicon nitride, a layercontaining silicon nitride oxide, or the like.

Then, the insulating layers 2, 5, 17, and 19 are etched byphotolithography so as to expose the release layer 100, thereby formingopenings 102 and 103 (FIG. 9A).

Then, an insulating layer 104 is formed by a known method (e.g., an SOGmethod or droplet discharge method) so as to cover the thin filmintegrated circuit 101 (FIG. 9B). The insulating layer 104 is formedusing an organic material, preferably an epoxy resin. The insulatinglayer 104 is formed to prevent the thin film integrated circuit 101 fromshattering. Since the thin film integrated circuit 101 is small, thin,and lightweight, it easily shatters after the removal of the releaselayer as it is not directly contact the substrate. However, by formingthe insulating layer 104 around the thin film integrated circuit 101,the weight of the thin film integrated circuit 101 can be increased, andthus the shattering thereof from the substrate 1 can be prevented. Thethin film integrated circuit 101 itself is thin and lightweight;however, by forming the insulating layer 104, the thin film integratedcircuit 101 can be prevented from being rolled and have a certain degreeof strength. Note that in the structure shown, the insulating layer 104is formed over the top surface and side surfaces of the thin filmintegrated circuit 101; however, the invention is not limited to thisstructure, and the insulating layer 104 may be formed only over the topsurface of the thin film integrated circuit 101. In addition, in theabove description, after the step of forming the openings 102 and 103,the step of forming the insulating layer 104 is carried out; however,the invention is not limited to this order. For example, after the stepof forming the insulating layer 104 over the insulating layer 19, thestep of forming the openings may be performed by etching the pluralityof insulating layers. In the case of this order of the steps, theinsulating layer 104 is formed over only the top surface of the thinfilm integrated circuit 101.

Then, an etchant is added into the openings 102 and 103, therebyremoving the release layer 100 (FIG. 10A). As the etchant, a gas or asolution containing halogen fluoride or an interhalogen compound isused. For example, chlorine trifluoride (ClF₃) is used as a gascontaining halogen fluoride. Thus, the thin film integrated circuit 101is separated from the substrate 1. Alternatively, the thin filmintegrated circuit 101 may be separated from the substrate 1 usingphysical strength without the use of an etchant.

Next, one surface of the thin film integrated circuit 101 is stuck to afirst base 105 so that the thin film integrated circuit 101 iscompletely separated from the substrate 1 (FIG. 10B).

Subsequently, the opposite surface of the thin film integrated circuit101 is stuck to a second base 106 so that the thin film integratedcircuit 101 is sealed with the first base 105 and the second base 106(FIG. 11). Thus, an IC tag is completed in which the thin filmintegrated circuit 101 is sealed by the first base 105 and the secondbase 106.

The first base 105 and the second base 106 each corresponds to a layeredfilm (formed of polypropylene, polyester, vinyl, polyvinyl fluoride,polyvinyl chloride, or the like); paper formed of a fibrous material; alayered film of a base film (e.g., polyester, polyamide, an inorganicvapor-deposited film, or paper) and an adhesive synthetic resin film(e.g., acrylic synthetic resin or epoxy synthetic resin); or the like.The layered film is stacked and attached on an object by thermalbonding. When stacking and attaching a layered film over an object, anadhesive layer provided on the outmost surface of the layered film or alayer (which is not an adhesive layer) provided on the outmost layer ismelted by heat treatment, and pressure is applied thereto forattachment.

Each surface of the first base 105 and the second base 106 may beprovided with an adhesive layer or no adhesive layer. The adhesive layercorresponds to a layer containing an adhesive agent such as athermosetting rein, an ultraviolet-curable resin, an epoxy resinadhesive or a resin additive.

Next, application examples of a semiconductor device which can transmitand receive data without contact will be described with reference todrawings. The semiconductor device which can transmit and receive datawithout contact is generally referred to as an RFID (Radio FrequencyIdentification) tag, an ID tag, an IC tag, an IC chip, an RF (RadioFrequency) tag, a wireless tag, an electronic tag, or a wireless chip inaccordance with an usage mode.

An RFID 80 has a function of transmitting and receiving data withoutcontact, and includes a power supply circuit 81, a clock generationcircuit 82, a data demodulation circuit 83, a data modulation circuit84, a control circuit 85 for controlling other circuits, a memorycircuit 86, and an antenna 87 (FIG. 12A). Further, the RFID may includea plurality of memory circuits rather than one memory circuit. An SRAM,a flash memory, a ROM, or a FeRAM or a circuit, which uses an organiccompound layer described in the above described embodiment modes in amemory element portion, and the like can be used.

Signals sent from a reader/writer 88 as radio waves are modulated intoalternating-current electric signals in the antenna 87 byelectromagnetic induction. Power supply voltage is generated in thepower supply circuit 81 by using the alternating-current electricsignals, and supplied to each circuit using a power supply line. Theclock generation circuit 82 generates various kinds of clock signalsbased on the alternating-current electric signals, which are inputtedfrom the antenna 87, and supplies the various kinds of clock signals tothe control signal 85. The modulation circuit 83 demodulates thealternating-current electric signals and supplies the demodulatedalternating-current electric signals to the control circuit 85. In thecontrol circuit 85, various kinds of arithmetic processings areperformed in accordance with the inputted signals. Programs, data andthe like that are used in the control circuit 85 are stored in thememory circuit 86. In addition, the memory circuit 86 can also be usedas a work area in the arithmetic processings. Then, data is transmittedto the modulation circuit 84 from the control circuit 85, and loadmodulation can be provided to the antenna 87 from the modulation circuit84 in accordance with the data. Consequently, the reader/writer 88receives load modulation applied to the antenna 87 via radio waves sothat the reader/writer can read the data.

In addition, the RFID may be of a type in that power supply voltage issupplied to each circuit via radio waves without using a power source (abuttery), or another type in that power supply voltage is supplied toeach circuit by utilizing both radio waves and a power source (abuttery).

A foldable RFID can be manufactured using such a structure described inthe above embodiment modes, and thus, such an RFID tag can be attachedto an object having a curbed surface.

Next, an example of usage mode of a flexible RFID will be described. Areader/writer 320 is provided on a side surface of a portable terminalwhich includes a display area 321. An RFID 323 is provided on a sidesurface of a product 322 (FIG. 12B). When the reader/writer 320 is heldto the RFID 323 included in the product 322, information about theproduct such as a raw material, a place of origin, test results in eachproduction process, history of distribution process, and a descriptionof a commodity, is displayed on the display area 321. In addition, whena commodity 326 is conveyed by a belt conveyor, the inspection of thecommodity 326 can be carried out using a reader/writer 324 and an RFID325 provided on the commodity 326 (FIG. 12C). In this way, by utilizingan RFID for a system, information can be easily obtained, therebyrealizing high performance and high added value. As described in theabove embodiment modes, even when an RFID is attached to an articlehaving a curved surface, a thin film transistor or the like included inthe RFID can be prevented from being damaged, so that a highly reliableRFID can be provided.

Other than those described above, the application range of a flexibleRFID tag is so wide that it may be applied to any product in order thatthe history object is revealed without contact and utilized inproduction, management and the like. For example, such an RFID tag maybe incorporated in bills, coins, securities, certificates, bearer bonds,containers for packages, books, recording media, personal belongings,vehicles, foods, clothes, healthcare items, livingware, medicals, andelectronic devices. Examples of these products are described withreference to FIGS. 13A to 13H.

The bills and coins include currency in the market and include a notethat is current as money in a specific area (cash voucher), memorialcoins, and the like. The securities include a check, a certificate, apromissory note, and the like (see FIG. 13A). The certificates include adriver's license, a resident card, and the like (see FIG. 13B). Thebearer bonds include a stamp, a rice coupon, various gift coupons, andthe like (see FIG. 13C). The containers for packages include paper forpacking a box lunch or the like, a plastic bottle, and the like (seeFIG. 13D). The books include a document and the like (see FIG. 13E). Therecording media include DVD software, a video tape, and the like (seeFIG. 13F). The vehicles include a wheeled vehicle such as a bicycle, avessel, and the like (see FIG. 13G). The personal belongings include abag, glasses, and the like (see FIG. 13H). The foods include food items,beverages, and the like. The clothes include clothing, footwear, and thelike. The healthcare items include a medical device, a health appliance,and the like. The livingware includes furniture, a lighting apparatus,and the like. The medicals include a medicine, an agricultural chemical,and the like. The electronic devices include a liquid crystal displaydevice, an EL display device, a television set (television receiver,thin television receiver), a cellular phone, and the like.

When an RFID tag 2000 is incorporated in bills, coins, securities,certificates, bearer bonds, and the like, forgery of them can beprevented. When an RFID tag is incorporated in containers for packages,books, recording media, personal belongings, foods, livingware,electronic devices and the like can be performed more efficiently, Whenan RFID tag is incorporated in vehicles, healthcare items, medicals, andthe like, forgery and theft of them can be prevented and medicines canbe prevented from being consumed in the wrong manner. An RFID tag may beattached to the surface of a product or incorporated into a product. Forexample, an RFID tag may be incorporated into paper of a book, or anorganic resin of a package. By using a flexible RFID tag having such astructure described in the above embodiment modes, damage or the like toan element included in the RFID tag can be prevented even when the RFIDtag is mounted on paper or the like.

Thus, when an RFD tag is incorporated in containers for packages,recording media, personal belongings, foods, clothes, livingware,electronic apparatuses, and the like, efficiency of inspection system,rental system, and the like can be increased. An RFID tag also preventsvehicles from being forged or stolen. In addition, when an RFID tag isimplanted into creatures such as animals, each creature can beidentified easily. For example, when an RFID tag is implanted intocreatures such as domestic animals, not only the year of birth, sex,breed and the like but also the health condition such as the currentbody temperature can be easily managed.

Note that, this embodiment mode can be freely combined with any of theabove embodiment modes. In other words, the present invention includesany combination of the configuration shown in the above embodiment modesand the configuration shown in this embodiment mode.

Embodiment Mode 4

This embodiment will describe an example of manufacturing a liquidcrystal display device (LCD) using the invention.

The manufacturing method of a display device described here is a methodof simultaneously manufacturing a pixel area including a pixel TFT and aTFT of a driver circuit area which is provided around the pixel area.Note that a CMOS circuit as a base unit is shown as a driver circuit tosimplify the description.

First, steps for forming a TFT shown in FIG. 14 are carried out inaccordance with the above embodiment mode. Note that parts that are thesame as those in the above embodiment mode are denoted by the samereference numerals. Note that in this embodiment mode, the pixel TFT 552is a multi-gate TFT.

After forming the interlayer insulating film 17 shown in FIG. 2D, aplanarization film which is to be a second interlayer insulating film 19is formed. As the planarization film, the one mentioned in the aboveembodiment mode can be used.

Next, contact holes are formed in the second interlayer insulating film19 and the interlayer insulating film 17 using resist masks.

A resist mask is formed over the second interlayer insulating film 19,and the second interlayer insulating film 19 and the interlayerinsulating film 17 are etched using the resist mask, so that a contacthole disposed on a source region and a contact hole disposed on a drainregion are formed.

After removing the resist mask and forming a conductive film, etching iscarried out using yet another resist mask, thereby wires 540 to 544 (asource wire or a drain wire or the like of the TFT). As the conductivefilm, a layered film of TiN, Al, and TiN or an Al alloy film or the likecan be used.

Here, the electrode or the wire is preferably led so as to have a roundcorner when seen from a direction perpendicular to the substrate 1. Bymaking the corners round, dust or the like can be prevented fromremaining at the corners of the wire; thus, the number of defectsgenerated due to dust can be reduced and yield can be improved.

A mask manufactured by exposure and development using a photosensitiveresist as a photomask is used for patterning. Transmittance of light forexposure is suppressed in an arbitrary portion of the photomask, therebythe thickness of the mask after development can be controlled. Bycontrolling the thickness of the mask, fine and accurate patterning canbe performed.

Next, a third interlayer insulating film 610 is formed over the secondinterlayer insulating film 19 and the wires 540 to 544. Note that thethird interlayer insulating film 610 can be formed using the samematerial to the second interlayer insulating film 19.

Next, a resist mask is formed using a photomask, and the thirdinterlayer insulating film 610 is partially removed by dry etching so asto form an opening (contact hole). In forming this contact hole, carbontetrafluoride (CF₄), oxygen (O₂) and helium (He) are used as the etchinggas. Note that the bottom of the contact hole reaches the electrode orwire 544.

Then, after removing the resist mask, a second conductive film is formedover the entire surface. Then, the second conductive film is patternedusing a photomask, thereby forming a pixel electrode 623, which iselectrically connected to the wire 544 (FIG. 14). When a reflectiveliquid crystal display panel is manufactured, the pixel electrode 623may be formed by sputtering using a light-reflective metal material suchas Ag (silver), Au (gold), Cu (copper), W (tungsten) or Al (aluminum).

In the case of manufacturing a transmissive liquid crystal displaypanel, the pixel electrode 623 is formed using a light-transmittingconductive film such as indium tin oxide (ITO), ITO containing siliconoxide, zinc oxide (ZnO) or tin oxide (SnO₂).

FIG. 16 is a magnified top view of a part of the pixel area including apixel TFT. A cross-sectional view taken along a solid line A-A′ of FIG.16 corresponds to a cross section of the pixel area in FIG. 14, andportions corresponding to those in FIG. 14 are denoted by the samereference numerals.

A pixel is provided at an intersection of a source signal line 543 and agate signal line 4802, and is provided with a transistor 552, acapacitor element 4804, and a liquid crystal element. Note that only oneof a pair of electrodes for driving liquid crystal of a liquid crystalelement (pixel electrode 623) is shown in the figure.

The transistor 552 includes a semiconductor layer 4806, a firstinsulating layer, and a part of the gate signal line 4802 which overlapswith the semiconductor layer 4806 with the first insulating layertherebetween. The semiconductor layer 4806 is to be an active layer ofthe transistor 552. The first insulating layer serves as a gateinsulating layer of the transistor. One of either the source or thedrain of the transistor 552 is connected to a source signal line 543through a contact hole 4807, and the other is connected to theconnection wire 544 through a contact hole 4808. The connection wire 544is connected to the pixel electrode 623 through a contact hole 4810. Theconnection wire 544 can be formed simultaneously with the source signalline 543 by patterning a conductive layer; which is also used forforming the source signal line 543.

The capacitor element 4804 is a capacitor element having a structureusing the semiconductor layer 4806 and a capacitor wire 4811 whichoverlaps with the semiconductor layer 4806 with the first insulatinglayer therebetween as a pair of electrodes, and the first insulatinglayer as a dielectric layer (referred to as a first capacitor element).Note that alternatively, the capacitor element 4804 may have a structureusing the capacitor wire 4811 and the pixel electrode 623 which overlapswith the capacitor wire 4811 with a second insulating layer therebetweenas a pair of electrodes, and the second insulating layer as a dielectriclayer (referred to as a second capacitor element). Since the secondcapacitor element is connected in parallel with the first capacitorelement, capacitance of the capacitor element 4804 can be increased byproviding the second capacitor element. Further, the capacitor wire 4811can be formed simultaneously with the gate signal line 4802 bypatterning a conductive layer, which is also used for forming the gatesignal line 4802.

A pattern used for patterning the semiconductor layer 4806, the gatesignal line 4802, the capacitor wire 4811, the source signal line 543,the connection wire 544, and the pixel electrode 623 has a shapechamfered by a side length of 10 μm or shorter in the corner. A resistmask is formed using the pattern of a photomask having that shape, andthe semiconductor layer 4806 is patterned using the resist mask; therebyforming a shape in which a corner of a pattern of the semiconductorlayer 4806 is chamfered. Note that the corners of the pattern of thesemiconductor layer 4806 may be further rounded. In other words, bysetting an exposure condition and an etching condition appropriately, apattern shape of the semiconductor layer 4806 may be smoothed more thanthe photomask pattern.

When a corner of a bent portion or a portion where line width changes issmoothed and rounded in a wire and an electrode, there are effectsdescribed below. When dry etching using plasma is performed, generationof fine particles due to abnormal discharge can be suppressed bychamfering a projecting portion. Even though the fine particles aregenerated, the fine particles can be prevented from accumulating at thecorner at the time of cleaning, and the fine particles can be washedaway by chamfering a convex portion. Thus, a problem of fine particlesor dust in the manufacturing process can be solved and the yield can beimproved.

Through the aforementioned steps, a TFT substrate of a liquid crystaldisplay device is completed, where the top-gate pixel TFT 552, the CMOScircuit 553 having the top-gate TFTs 550 and 551, and the pixelelectrode 623 are formed over the substrate. Although a top-gate TFT isformed in this embodiment, a bottom-gate TFT may be used as appropriate.

Then, an alignment film 624 a is formed covering the pixel electrode623. The alignment film 624 a may be formed by a droplet dischargemethod, screen printing or an offset printing. After that, the surfaceof the alignment film 624 a is rubbed.

A color filter including a color layer 626 a, a light-shielding layer(black matrix) 626 b and an overcoat layer 627 is provided over acounter substrate 625, and a light-transmitting or reflective counterelectrode 628 and an alignment film 624 b are formed thereover. Then, asealant 600 having a closed pattern is formed by a droplet dischargemethod so as to surround a region overlapping the pixel area 650including a pixel TFT (FIG. 17A). Since liquid crystal is dropped here,an example of applying the sealant 600 so as to form a closed pattern isshown. Alternatively, a dip method (pumping method) may be used, inwhich liquid crystal is introduced into the space between the substratesby utilizing capillary action after attaching the substrate 500 to thecounter substrate 625.

Then, a liquid crystal composition 629 is dropped under reduced pressureso that bubbles are not mixed therein (FIG. 17B), thereby attaching thesubstrates 500 and 625 to each other (FIG. 17C). The liquid crystalcomposition 629 is dropped once or a plurality of times into the sealpattern having a closed loop. As an alignment mode of the liquid crystalcomposition 629, a TN mode is used in which the alignment of liquidcrystal molecules is twist at 90° from where light enters to where lightis emitted. The substrates are attached to each other in such a mannerthat the rubbing directions thereof are perpendicular to each other.

The distance between the pair of the substrates may be kept even bydispersing spherical spacers or forming a columnar spacer formed of aresin, or by mixing fillers in the sealant 600. The aforementionedcolumnar spacer is formed of an organic resin material containing atleast one of acrylic, polyimide, polyimide amide, or epoxy as a maincomponent, or an inorganic material having one of silicon oxide, siliconnitride and silicon oxide containing nitrogen, or a layered filmthereof.

Then, the substrate is sectioned. In the case of obtaining amultiplicity of panels from one substrate, the substrate is sectionedinto each panel. On the other hand, in the case of obtaining one panelfrom one substrate, a sectioning step may be omitted by attaching acounter substrate which is cut in advance to the substrate (FIG. 15 andFIG. 17D).

Then, an FPC (Flexible Printed Circuit) is attached to an anisotropicconductive layer using a known technique. Through the aforementionedsteps, a liquid crystal display device is completed. In addition, anoptical film is attached if necessary. In the case of manufacturing atransmissive liquid crystal display device, a polarizing plate isattached to each of the TFT substrate and the counter substrate.

FIG. 18A shows a top view of a liquid crystal display device obtainedthrough the aforementioned steps, and FIG. 18B shows an example of a topview of another liquid crystal display device.

In FIG. 18A, reference numeral 1 denotes a TFT substrate, 625 denotes acounter substrate, 650 denotes a pixel area, 600 denotes a sealant and801 denotes an FPC. Here, a liquid crystal composition is discharged bya droplet discharge method, and the pair of the substrates 500 and 625are attached to each other with the sealant 600 under the reducedpressure.

In FIG. 18B, reference numeral 1 denotes a TFT substrate, 625 denotes acounter substrate, 802 denotes a source signal line driver circuit, 803denotes a gate signal line driver circuit, 650 denotes a pixel area, 600a denotes a first sealant, 600 b denotes a second sealant, and 801denotes an FPC. Here, a liquid crystal composition is discharged by adroplet discharge method, and the pair of the substrates 500 and 625 areattached to each other with the first sealant 600 a and the secondsealant 600 b. Since liquid crystal is not required in the drivercircuit areas 802 and 803, liquid crystal is held only in the pixel area650, and the second sealant 600 b is provided for reinforcement of thewhole panel.

As described above, in this embodiment, a liquid crystal display devicecan be manufactured using a TFT using the invention. Accordingly, themanufacturing time and cost can be reduced. The liquid crystal displaydevice manufactured in this embodiment can be used as display portionsof various electronic devices.

Note that although a top-gate TFT is used as the TFT in this embodiment,the invention is not limited to this structure, and a bottom-gate(inverted staggered) TFT or a staggered TFT may be used as appropriate.Further, the invention is not limited to a multi-gate TFT, and asingle-gate TFT may be used.

This embodiment can be freely combined with any of the aforementionedembodiment modes as required.

Embodiment Mode 5

This embodiment mode will describe an example of manufacturing a lightemitting device according to the present invention.

First, steps for forming a TFT shown in FIG. 19 are finished inaccordance with the above embodiment mode. Note that parts that are thesame as those in the above embodiment mode are denoted by the samereference numerals. Note that FIG. 19 shows only one of TFTs.

After forming an interlayer insulating film 17, a planarization film tobe a second interlayer insulating film 19 is formed. As theplanarization film, one described in the above embodiment mode can beuse (FIG. 19A).

a contact hole is formed in the second interlayer insulating film 19 andthe interlayer insulating film 17 using a resist mask.

Next, the contact hole that reach a semiconductor layer are formed. Thecontact holes can be formed by etching using a resist mask until thesemiconductor layer is exposed. Either wet etching or dry etching can becarried out. The etching may be conducted once or a plurality of timesdepending on the condition. When the etching is conducted a plurality oftimes, both wet etching and dry etching may be conducted (FIG. 19B).

Then, a conductive layer is formed so as to cover the contact holes andthe first interlayer insulating layer 17. A connection portion 61 a, awire 61 b, and the like are formed by processing the conductive layerinto a desired shape. This wire may be a single layer of aluminum;copper; an alloy of aluminum, carbon, and nickel; an alloy of aluminum,carbon, and molybdenum; or the like. Alternatively, the wire may beformed in a layered structure of molybdenum, aluminum, molybdenum in theorder from the substrate. Alternatively, a structure of titanium,aluminum, titanium or titanium, titanium nitride, aluminum, titanium canalso be used (FIG. 19D).

A third interlayer insulating layer 163 is formed to cover theconnection portion 161 a, the wire 161 b, and the second interlayerinsulating layer 19. As the material of the third interlayer insulatinglayer 163, a self-planarizing coating formed of acrylic, polyimide,siloxane, or the like is preferably used. In this embodiment mode, thethird interlayer insulating layer 163 is formed of siloxane (FIG. 19D).

Next, an insulating layer may be formed of silicon nitride over thethird interlayer insulating layer 163. This is formed to prevent thethird interlayer insulating layer 163 from being etched more thannecessary in a later step of etching a pixel electrode. Therefore, theinsulating layer is not necessary when the difference is large betweenthe etching rates of the pixel electrode and the second interlayerinsulating layer.

Next, a contact hole penetrating the third interlayer insulating layer163 to reach the connection portion 61 a is formed.

After a light-transmitting conductive layer is formed so as to cover thecontact hole and the third interlayer insulating layer 163 (or theinsulating layer), the light-transmitting conductive layer is processedto form the first electrode 164 of the thin film light emitting element.Here, the first electrode 164 electrically contacts the connectionportion 161 a.

The first electrode 164 can be formed from a material of a conductivemetal such as aluminum (Al), silver (Ag), gold (Au), platinum (Pt),nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe),cobalt (Co), copper (Cu), palladium (Pd), lithium (Li), cesium (Cs),magnesium (Mg), calcium (Ca), strontium (Sr), or titanium (Ti); an alloythereof such as aluminum-Si (Al—Si), aluminum-titanium (Al—Ti), oraluminum-silicon-copper (Al—Si—Cu); a nitride of a metal material suchas titanium nitride (TiN), a metal compound such as indium tin oxide(indium tin oxide), ITO containing silicon, IZO (indium zinc oxide) inwhich 2% to 20% of zinc oxide (ZnO) is mixed in indium oxide, or thelike.

An electrode through which light is emitted may preferably be formedusing a light-transmitting conductive film. For example, a metalcompound such as ITO (indium tin oxide), ITO containing silicon (ITSO),or IZO (indium zinc oxide) in which zinc oxide (ZnO) is mixed in indiumoxide can be used. Alternatively, an extremely thin film of metal suchas Al or Ag is used. When light is emitted through a second electrode, ahighly-reflective material (e.g., Al, Ag or the like) can be used forthe first electrode 164. In this embodiment mode, ITSO is used for thefirst electrode 164 (FIG. 20A).

Next, an insulating layer formed of an organic material or an inorganicmaterial is formed so as to cover the third interlayer insulating layer163 (or the insulating layer) and the first electrode 164. Subsequently,the insulating layer is processed so as to partially expose the firstelectrode 164, thereby forming a partition wall 165. As the material ofthe partition wall 165, a photosensitive organic material (such asacrylic or polyimide) is preferable. Alternatively, a non-photosensitiveorganic or inorganic material may also be used. Further, the partitionwall 165 may be used as a black matrix by making the partition wall 165black in such a way that a black pigment or dye such as titanium blackor carbon nitride is diffused into the material of the partition wall165 using a dispersant or the like. It is desirable that the partitionwall 165 has a tapered shape where its end surface toward the firstelectrode has curvature changing continuously (FIG. 20B).

Next, a layer containing a light emitting material 166 is formed, and asecond electrode 167 covering the layer containing a light emittingsubstance 166 is formed 6 subsequently. Thus, a light emitting element193 in which the layer 166 containing a light emitting substance issandwiched between the first electrode 164 and the second electrode 1677and light emission can be obtained by applying a higher voltage to thefirst electrode than the second electrode (FIG. 20C). For an electrodematerial used for forming the second electrode 167, the same material asthe material of the first electrode can be used. Aluminum is used forthe second electrode in this embodiment mode.

Further, the layer containing a light emitting substance 166 is formedby vapor deposition, an ink-jet method, spin coating, dip coating, orthe like. The layer 66 containing a light emitting material may be alaminate of layers having various functions such as a hole transport,hole injection, electron transport, electron injection, light emission,or may be a single layer of a light emitting layer.

In the case of an inorganic electroluminescent display device,fluorescent material particles dispersed in a dispersant can be used fora layer containing a light-emitting material 166.

The fluorescent material in which a donor impurity such as Cl(chlorine), I (iodine), or Al together with is Cu (copper) are added toZnS can be used.

As the dispersant, a polymer having a relatively high dielectricconstant such as a cyanoethyl cellulose-based resin, or a resin such asa resin based on polyethylene, polypropylene, or polystyrene; a siliconeresin; an epoxy resin; or a vinylidene fluoride resin can be used. Fineparticles of BaTiO₃ (barium titanate) or SrTiO₃ (titanate strontium)which has high dielectric constant are mixed appropriately in the resinto control the dielectric constant. As a dispersing means, an ultrasonicdisperser or the like can be used.

A dielectric layer may be provided between the layer containing alight-emitting material 166 and one of the electrodes. For thedielectric layer, any material can be used as long as it is a highlydielectric and highly insulating material which also has high dielectricbreakdown voltage. For example, one selected from metal oxides ornitrides, for example, TiO₂, BaTiO₃, SrTiO₃, PbTiO₃, KNO₃, PbNbO₃,Ta₂O₃, BaTa₂O₆, LiTaO₃, Y₂O₃, Al₂O₃, ZrO₂AlON, or ZnS is used.

In the case of an inorganic electroluminescent display device, thelight-emitting layer may be sandwiched between insulating layers to havea double insulation structure. The light-emitting layer can use a II-VIcompound such as ZnS (zinc sulfide) which contains Mn (manganese) or arare earth element, and the insulating layer can use oxides or nitridessuch as Si₃N₄, SiO₂, Al₂O₃, or TiO₂.

Further, a single layer or a stack of an organic compound may be usedfor a layer containing a light-emitting material. In addition, aninorganic compound may be added to a part of a layer containing anorganic compound to form a layer which is in contact with the first orsecond electrode.

After that a silicon oxide film containing nitrogen is formed as apassivation, film by plasma CVD. In the case of using the silicon oxidefilm containing nitrogen, a silicon oxynitride film manufactured usingSiH₄, N₂O, and NH₃ by plasma CVD, a silicon oxynitride film manufacturedusing SiH₄ and N₂O by plasma CVD, or a silicon oxynitride filmmanufactured by plasma CVD using a gas in which SiH₄ and N₂O are dilutedwith Ar may be preferably formed.

As the passivation film, a silicon oxynitride hydride film manufacturedusing SiH₄, N₂O, and H₂ is also applicable. Naturally, the structure ofa first passivation film is not limited to a single-layer structure, andthe passivation film may be formed in a single-layer structure or alayered structure including another insulating layer containing silicon.A multilayer film of a carbon nitride film and a silicon nitride film, amultilayer film including a styrene polymer, a silicon nitride film, ora diamond-like carbon film may be formed instead of a silicon oxide filmcontaining nitrogen.

Subsequently, in order to protect the light emitting element from adeterioration-promoting material such as water, the display area issealed. In the case of using a counter substrate for the sealing, thecounter substrate and an element substrate are attached together with aninsulating sealing material so as to expose an external connectionportion. The space between the counter substrate and the elementsubstrate may be filled with an inert gas such as dry nitrogen, or thewhole surface of the pixel area may be coated with the sealing materialfor attaching the counter substrate. It is preferable to use anultraviolet curable resin or the like for the sealing material. A dryingagent or particles for keeping the gap between the substrates uniformmay be mixed into the sealing material. Subsequently, a flexible wiresubstrate is pasted on the external connection portion, therebycompleting a light emitting device.

An example of the structure of the thus manufactured light emittingdevice will be described with reference to FIGS. 21A and 21B. Althoughthe shapes are different, parts having the same functions are denoted bythe same reference numerals and the description thereof may be omitted.In this embodiment mode, the thin film transistor 170 connects to thelight emitting element 193 via the connection portion 161 a.

In FIG. 21A, the first electrode 164 is formed of a light-transmittingconductive film and has a structure in which light emitted from a lightemitting layer containing the light emitting substance 166 is extractedfrom the substrate 1 side. Reference numeral 194 denotes a countersubstrate, which is to be fixed to the substrate 1 with a sealingmaterial or the like after forming the light emitting element 193. Byfilling the space between the counter substrate 194 and the element witha light-transmitting resin 188 or the like and sealing the space, it ispossible to prevent the light emitting element 193 from deterioratingdue to moisture. Further, the resin 188 desirably has hygroscopicity. Inaddition, it is more desirable that a desiccant 189 having highlight-transmitting properties is diffused in the resin 188, so that theeffect of moisture can be further suppressed.

In FIG. 21B, each of the first electrode 164 and the second electrode167 is formed with a light-transmitting conductive film, and light canbe extracted from both the substrate 1 and the counter substrate 194.With this structure, it is possible to prevent the screen from beingtranslucent by separately providing polarizing plates 190 outside thesubstrate 1 and the counter substrate 194, whereby increasing thevisibility. A protective film 191 is preferably provided outside thepolarizing plate 190.

Either an analog video signal or a digital video signal may be used inthe light emitting device using the present invention. The digital videosignal includes a video signal using voltage and a video signal usingcurrent. When the light emitting element emits light, the video signalinputted into a pixel uses a constant voltage or a constant current.When the video signal uses a constant voltage, the voltage applied tothe light emitting element or the current flowing in the light emittingelement is constant. Meanwhile, when the video signal uses a constantcurrent, the voltage applied to the light emitting element or thecurrent flowing in the light emitting element is constant. The lightemitting element to which a constant voltage is applied is driven byconstant voltage driving, and the light emitting element in which theconstant current flows is driven by the constant current driving.Constant current flows in the light emitting element driven by theconstant current driving without being affected by the change in theresistance of the light emitting element. Whichever of the drivingmethods described above can be used for a light emitting device or adriving method according to the present invention.

A light emitting device according to the present invention having such astructure is a highly reliable light emitting device since hydrogen ionsthat are generated in addition to impurity ions are prevented frompenetrating into the channel region.

This embodiment can be combined with an appropriate structure of any ofthe above embodiment modes.

Embodiment Mode 6

This embodiment will describe an appearance of a panel which is a lightemitting device of the present invention with reference to FIGS. 22A and22B. FIG. 22A is a top view of a panel in which transistors and lightemitting elements are formed over a substrate 4001 is sealed with asealing material formed between the substrate 4001 and a countersubstrate 4006. FIG. 22B is a cross-sectional view corresponding to FIG.22A. The light emitting element mounted on this panel has a structure asdescribed in the above embodiment mode.

A sealing material 4005 is provided so as to surround a pixel area 4002,a signal line driver circuit 4003, and a scan line driver circuit 4004which are provided over a substrate 4001. In addition, the countersubstrate 4006 is provided over the pixel area 4002, the signal linedriver circuit 4003, and the scan line driver circuit 4004. Thus, thepixel area 4002, the signal line driver circuit 4003, and the scan linedriver circuit 4004 together with a filler 4007 are scaled with thesubstrate 4001, the sealing material 4005, and the counter substrate4006.

The pixel area 4002, the signal line driver circuit 4003, and the scanline driver circuit 4004 provided over the substrate 4001 have aplurality of thin film transistors. FIG. 22B shows a thin filmtransistor 4008 included in the signal line driver circuit 4003 and athin film transistor 4010 included in the pixel area 4002.

The light emitting element 4011 is electrically connected to the thinfilm transistor 4010.

Further, a lead wire 4014 corresponds to a wire for supplying a signalor power source voltage to the pixel area 4002, the signal line drivercircuit 4003, and the scan line driver circuit 4004. The lead wire 4014is connected to a connection terminal 4016 through a lead wire 4015. Theconnection terminal 4016 is electrically connected to a terminal of aflexible printed circuit (FPC) 4018 through an anisotropic conductivefilm 4019.

As the filler 4007, other than inert gas such as nitrogen or argon, anultraviolet curable resin or a thermosetting resin can be used. Forexample, polyvinyl chloride, acrylic, polyimide, an epoxy resin, asilicone resin, polyvinyl butyral, or ethylene vinylene acetate can beused.

It is to be noted that the light emitting device according to thepresent invention includes in its category the panel in which the pixelarea having the light emitting elements is formed and a module in whichan IC is mounted on the panel.

This embodiment can be used in appropriate combination with a structureof any one of the above embodiment modes as appropriate.

Embodiment Mode 7

This embodiment will describe a pixel circuit and a protective circuitin the panel and the module shown in Embodiment Mode 6, and theiroperations. FIGS. 19A to 22B are cross sectional views of a driving TFT1403 or a switching TFT 1401 and a light emitting element 1405 shown inFIGS. 23A to 23F.

A pixel shown in FIG. 23A includes a signal line 1410 and power sourcelines 1411 and 1412 in columns and a scan line 1414 in a row. The pixelfurther includes a switching TFT 1401, the driving TFT 1403, a currentcontrol TFT 1404, a capacitor 1402, and the light emitting element 1405.

A pixel shown in FIG. 23C has the same structure as one in FIG. 23Aexcept for that a gate electrode of the driving TFT 1403 is connected tothe power source line 1412 provided in a row. In other words, the pixelsshown in FIGS. 23A and 23C have the same equivalent circuit diagram.However, in the case of arranging the power source line 1412 in thecolumn direction (FIG. 23A) and in the case of arranging the powersource line 1412 in the row direction (FIG. 23C), each power source lineis formed using a conductive film in different layers. Here, attentionis paid to a wire connected to the gate electrode of the driving TFT1403, and the structure is shown separately in FIGS. 23A and 23C inorder to show that these wires are manufactured in different layers.

As a feature of the pixels shown in FIGS. 23A and 23C, the driving TFT1403 and the current control TFT 1404 are connected serially within thepixel, and it is preferable to set the channel length L (1403) and thechannel width W (1403) of the driving TFT 1403, and the channel lengthL(1404) and the channel width W (1404) of the current control TFT so asto satisfy L (1403)/W (1403):L (1404)/W (1404)=5 to 6000:1.

The driving TFT 1403 operates in a saturation region and serves tocontrol the current value of the current flowing into the light emittingelement 1405. The current control TFT 1404 operates in a linear regionand serves to control the current supplied to the light emitting element1405. Both the driving TFT 1403 and the current control TFT 1404preferably have the same conductivity type considering the manufacturingprocess, and the driving TFT 1403 and the current control TFT 1404 aren-channel type TFTs in this embodiment mode. The driving TFT 1403 may beeither an enhancement mode TFT or a depletion mode TFT. Since thecurrent control TFT 1404 operates in the linear region in a lightemitting device having the above structure according to the presentinvention, slight fluctuation in Vgs of the current control TFT 1404does not affect the current value of the light emitting element 1405. Inother words, the current value of the light emitting element 1405 can bedetermined by the driving TFT 1403 operating in the saturation region.With the above structure, variation in the luminance of the lightemitting element due to the variation in the characteristics of the TFTcan be reduced, thereby providing a light emitting device in which theimage quality is improved.

In the pixels shown in FIGS. 23A to 23D, the switching TFT 1401 is tocontrol input of the video signal to the pixel, and the video signal isinputted into the pixel when the switching TFT 1401 is turned ON. Then,the voltage of the video signal is held in the capacitor 1402. AlthoughFIGS. 23A and 23C show the structure in which the capacitor 1402 isprovided, the present invention is not limited thereto. When the gatecapacitance or the like can serve as a capacitor holding the videosignal, the capacitor 1402 is not necessarily provided.

A pixel shown in FIG. 23B has the same pixel structure as that in FIG.23A except for that a TFT 1406 and a scan line 1414 are added.Similarly, a pixel shown in FIG. 23D has the same pixel structure asthat in FIG. 23C expect that the TFT 1406 and the scan line 1414 areadded.

ON and OFF of the TFT 1406 is controlled by the additionally providedscan line 1414. When the TFT 1406 is turned ON, the charge held in thecapacitor 1402 is discharged; thus, the current control TFT 1404 isturned OFF. In other words, by the provision of the TFT 1406, a statecan be produced forcedly in which the current does not flow into thelight emitting element 1405. For this reason, the TFT 1406 can bereferred to as an eraser TFT. Consequently, in the structures shown inFIGS. 23B and 23D, a lighting period can be started at the same time asor just after the start of a writing period before the writing of thesignal into all the pixels; therefore the duty ratio can be improved.

In a pixel shown in FIG. 23E, the signal line 1410 and the power sourceline 1411 are arranged in the column direction, and the scan line 1414is arranged in the row direction. Further, the pixel includes theswitching TFT 1401, the driving TFT 1403, the capacitor 1402, and thelight emitting element 1405. A pixel shown in FIG. 23F has the samepixel structure as one shown in FIG. 23E except for that the TFT 1406and a scan line 1415 are added. In the structure shown in FIG. 23F, theduty ratio can also be increased by the provision of the TFT 1406.

As thus described, various kinds of pixel circuits can be used. Inparticular, in the case of forming a thin film transistor from anamorphous semiconductor film, the semiconductor film of the driving TFT1403 is preferably large. In the case where the semiconductor is large,in the above pixel circuit, a top emission type is preferable in whichlight from the light emitting element is extracted from the countersubstrate.

Such an active matrix light emitting device can be driven at a lowvoltage when the pixel density increases, since the TFT is provided ineach pixel, which is considered advantageous.

Although this embodiment describes the active matrix light emittingdevice in which a TFT is provided in each pixel, a passive matrix lightemitting device can also be formed in which TFTs are provided in eachcolumn. Since TFTs are not provided in each pixel in a passive matrixlight emitting device, high aperture ratio can be obtained. In the caseof a light emitting device in which light is emitted from both sides ofthe light emitting stack, the transmittance of the passive matrix lightemitting device is increased.

Subsequently, a case where a diode is provided as a protective circuiton the scan line and the signal line with the use of an equivalentcircuit shown in FIG. 23E will be described.

In FIG. 24, the switching TFT 1401, the driving TFT 1403, the capacitor1402, and the light emitting element 1405 are provided in a pixel area1500. Diodes 1561 and 1562 are provided on the signal line 1410. In thesimilar way to the switching TFT 1401 or the driving TFT 1403, thediodes 1561 and 1562 are manufactured based on the above embodiments,and have a gate electrode, a semiconductor layer, a source electrode, adrain electrode, and the like. The diodes 1561 and 1562 are operated asdiodes by connecting the gate electrode with the drain electrode or thesource electrode.

Wires 1554 and 1555 connecting to the diodes are formed using the samelayer as the gate electrode. Therefore, in order to connect the wires1554 and 1555 with the source electrode or the drain electrode of thediode, it is necessary to form a contact hole in the gate insulatinglayer.

A diode provided on the scan line 1414 has the similar structure.

As thus described, according to the present invention, protective diodesprovided in an input stage can be manufactured simultaneously. Theposition where the protective diode is formed is not limited to this,and the diode may also be provided between the driver circuit and thepixel.

This embodiment can be combined with a suitable structure of the aboveembodiment modes as appropriate.

Embodiment Mode 8

As electronic device having light emitting devices according to thepresent invention mounted with modules shown as examples in the aboveembodiment modes, a camera such as a video camera and a digital camera;a goggle type display (a head mounted display); a navigation system; anaudio reproducing device (e.g., a car audio component); a computer; agame machine; a portable information terminal (e.g., a mobile computer,a cellular phone, a portable game machine, an electronic book, or thelike); an image reproducing device equipped with a recording medium(specifically, a device which can reproduce the content of a recordingmedium such as a digital versatile disc (DVD) and which has a displayfor displaying an image stored therein); and the like can be given.Specific examples of these electronic appliances are shown in FIGS. 25Ato 25E, and FIG. 26.

FIG. 25A shows a monitor for a television receiver or a personalcomputer, or the like, including a housing 3001, a display area 3003,speakers 3004, and the like. An active matrix display device is providedin the display area 3003. Each pixel of the display area 3003 includes aTFT manufactured in accordance with the present invention. By using theTFT of the present invention, a television with less characteristicdeterioration can be obtained.

FIG. 25B shows a cellular phone, including a main body 3101, a housing3102, a display area 3103, an audio input portion 3104, an audio outputportion 3105, operation keys 3106, an antenna 3108, and the like. Anactive matrix display device is provided in the display area 313. Eachpixel of the display area 3103 includes a TFT manufactured in accordancewith the present invention. By using the TFT of the present invention, acellular phone with less characteristic deterioration can be obtained.

FIG. 25C shows a computer, including a main body 3201, a housing 3202, adisplay area 3203, a keyboard 3204, an external connection port 3205, apointing mouse 3206, and the like. An active matrix display device isprovided in the display area 3203. Each pixel of the display area 3203includes a TFT manufactured in accordance with the present invention. Byusing the TFT of the present invention, a computer with lesscharacteristic deterioration can be obtained.

FIG. 25D shows a mobile computer, including a main body 3301, a displayarea 3302, a switch 3303, operation keys 3304, an infrared port 3305,and the like. An active matrix display device is provided in the displayarea 3302. Each pixel of the display area 3302 includes a TFTmanufactured in accordance with the present invention. By using the TFTof the present invention, a mobile computer with less characteristicdeterioration can be obtained.

FIG. 25E shows a portable game machine, including a housing 3401, adisplay area 3402, speaker portions 3403, operation keys 3404, arecording medium insert portion 3405, and the like. An active matrixdisplay device is provided in the display area 3402. Each pixel of thedisplay area 3402 includes a TFT manufactured in accordance with thepresent invention. By using the TFT of the present invention, a portablegame machine with less characteristic deterioration can be obtained.

FIG. 26 shows a flexible display, including a main body 3110, a pixelarea 3111, a driver IC 3112, a receiving device 3113, a film buttery3114, and the like. The receiving device 3113 can receive a signal froman infrared communication port 3107 of the above described cellularphone. An active matrix display device is provided in the pixel area3111. Each pixel of the pixel area 3111 includes a TFT manufactured inaccordance with the present invention. By using the TFT of the presentinvention, a flexible display with less characteristic deterioration canbe obtained.

As set forth above, the application range of the present invention isextremely wide, and the present invention can be applied to electronicdevices in all fields.

Embodiment

This embodiment will describe a TFT which was manufactured in a mannerdescribed in Embodiment Mode 1 and the characteristics measured.

As shown in FIG. 5A, a silicon nitride oxide film 51 was formed as abase insulating film over an alkali-free glass substrate (AN100 producedby Asahi Glass Co., Ltd.) 50 to a thickness of 50 nm by plasma CVD, andafter that, a silicon oxynitride film 52 was formed to a thickness of100 nm by plasma CVD.

Next, an amorphous silicon film 53 was formed to a thickness of 50 nm byplasma CVD.

Next, an amorphous silicon film 53 was crystallized. First, as shown inFIG. 5B, a metal containing layer 54 was formed on the surface of theamorphous silicon film 53. The metal containing layer 54 was formed bycoating with an acetic acid nickel solution containing 10 ppm of nickelby weight using a spinner.

Next, the substrate 50, the amorphous silicon film 53, and the metalcontaining layer 54 were heat treated. Here, a crystalline silicon film49 was formed through heat treatment by rapid thermal annealing (RTA).

Then, as shown in FIG. 5C, the crystalline silicon film 49 wasirradiated with laser light 55 under atmospheric pressure, therebyincreasing the crystallinity of the crystalline silicon film 49 (ratioof crystal components against the whole volume of the film), andrepairing defects remaining in the crystal grains.

For the laser light, a XeCl excimer laser which is a pulsed laser wasused. The repetition rate was 30 Hz, and the energy density wasapproximately 300 mJ/cm² to 500 mJ/cm². The silicon film was movedrelatively to the laser beam at a speed of 0.5 cm/s to 10 cm/s so as tobe irradiated. The overlap ratio was set at 95% or more.

Next, the surface of the crystalline silicon film 49 was treated with anozone containing solution (typically, ozone water), thereby forming anoxide film (referred to as chemical oxide) on the surface of thecrystalline silicon film 49. Thus, a barrier layer 56 formed from anoxide film having a thickness of 1 nm to 10 nm in total was formed. Thebarrier layer 56 functioned as an etching stopper when only a getteringlayer was selectively removed in a later step.

Next, a gettering layer 57 containing an argon element was formed as agettering site on the barrier layer 56. Here, an amorphous silicon filmcontaining argon gas was formed as the gettering layer 57 by sputtering.

Next, the crystalline silicon film 49, the barrier layer 56, and thegettering layer 57 were heat treated by RTA. Thus, as shown by the arrowin FIG. 5D, the metal element (for example, nickel) was gettered,thereby reducing the concentration of the metal element in thecrystalline silicon film 49.

Only the gettering layer 57 was selectively removed by a known etchingmethod using the barrier layer 56 as an etching stopper. After that, thebarrier layer 56 formed from an oxide film was removed using, forexample, an etchant containing hydrofluoric acid (FIG. 5E). Through theabove steps, the crystalline silicon film 49 was obtained.

Next, channel doping was performed using p-type impurity ionsconsidering the threshold characteristics of a TFT to be formed. Theaccelerating voltage was 15 kV, and the dose was 1.5×10¹³ atoms/cm².

Next, the crystalline silicon film was formed into island-shapedcrystalline silicon films 58 and 59 by a known photolithography process(FIG. 6A). Here, a p-channel TFT was formed using the crystallinesilicon film 58, and an n-channel TFT was formed using the crystallinesilicon film 59.

Next, after the surface of the crystalline silicon film was cleaned withan containing etchant hydrofluoric acid, a silicon oxide film was formedas a gate insulating film 74 over the crystalline silicon film to athickness of 100 nm by plasma CVD (FIG. 6B).

Next, after cleaning the surface of the gate insulating film 74, atantalum nitride (TaN) film 60 was formed to a thickness of 30 nm bysputtering and a W film 61 was formed by sputtering as conductive filmsfor forming a gate electrode, over the whole surface including thesurface of the gate insulating film 74 (FIG. 6B). The W film 61 wasformed to a thickness of 170 nm or 220 nm.

A photoresist film was formed on the W film 61 by coating, and thephotoresist film was exposed and developed, thereby forming a firstresist mask 62 a and a second resist mask 62 b respectively above thecrystalline silicon films 58 and 59 to thicknesses of 1.0 μm to 1.5 μm(FIG. 6B). Here, a novolac-naphthoquinone diazide based resist was used.The W film and the TaN film were etched by dry etching using the resistmasks 62 a and 62 b, thereby manufacturing gate electrodes 63 a and 63b. A mixture of CF₄ and Cl₂ was used as the etching gas, and O₂ gas maybe further mixed therein as necessary.

Next, a part of the gate insulating film was dry etched using the resistmasks 62 a and 62 b, and the gate electrodes 63 a and 63 b as masks sothat the gate insulating film was made thin. CHF₃ gas was used as theetching gas. Thus, the thicknesses of the gate insulating films over theregions which were not masked with the gate electrodes 63 a and 63 b,namely, areas to be a source region and a drain region were 80 mm.

Next, a photoresist film of a novolac-naphthoquinone diazide based resinwas formed by coating, and the photoresist film was exposed anddeveloped, thereby forming a third resist mask 64 to a thickness of 1.0μm to 1.5 μm so as to cover the crystalline silicon film 59, the gateelectrode 63 b, and the second resist mask 62 b (FIG. 6D).

P-type impurity ion (ions containing B) 65 were added to the crystallinesilicon film 58 by an ion shower doping method using the first resistmask 62 a, the second resist mask 62 b, the third resist mask 64, andthe gate electrodes 63 a and 63 b as masks, at a dose of 2.5×10¹⁶atoms/cm², thereby forming a source region 66 and a drain region 67(FIG. 6D). Further, the concentration of the p-type impurity near thesurfaces of the source region 66 and the drain region 67 wasapproximately 3.0×10²⁰ cm⁻³. The accelerating voltage of the p-typeimpurity ions was set at 80 kV. Diborane (B₂H₆) gas diluted withhydrogen gas was used.

Next, the third resist mask 64, the first resist mask 62 a, and thesecond resist mask 62 b were removed by ashing using O₂.

Next, a photoresist film of a novolac-naphthoquinone diazide based resinwas formed by coating, and the photoresist film was exposed anddeveloped, thereby forming a fourth resist mask 68 to a thickness of 1.0μm to 1.5 μm so as to cover the crystalline silicon film 59 and the gateelectrode 63 b (FIG. 7A).

N-type impurity ions (ions containing phosphorus) 69 were added to thecrystalline silicon film 59 by a plasma doping method using the fourthresist mask 68 and the gate electrodes 63 a and 63 b as masks at a lessdose of 3.0×10¹⁵ atoms/cm² than the p-type impurity ions, therebyforming a source region 70 and a drain region 71 (FIG. 7B). Further, theconcentration of the n-type impurity near the surfaces of the sourceregion 70 and the drain region 71 was approximately 1.3×10²⁰ cm⁻³. Theaccelerating voltage of the n-type impurity ions was set at 65 kV whichwas lower than the accelerating voltage of the p-type impurity ions.Phosphine (PH₃) gas diluted with hydrogen gas was used. Thus, ap-channel TFT was formed using the crystalline silicon film 58, and ann-channel TFT was formed using the crystalline silicon film 59. Notethat the channel length (L) of the TFT was 10 μm, and the channel width(W) thereof was 8 μm.

Next, the fourth resist mask 68 was removed by ashing using O₂.

Next, a silicon nitride film 72 was formed to a thickness of 100 nm byplasma CVD so as to cover the whole surface including the gateinsulating film 74 and the gate electrodes 63 a and 63 b, andhydrogenation was performed in a nitrogen atmosphere at 410° C. for onehour.

Next, a resist mask was formed over the silicon nitride film 72, and thesilicon nitride film 72 was etched by wet etching using the resist mask,thereby forming contact holes separately disposed on each of the sourceregions 66 and 67 and the drain regions 70 and 71.

After removing the resist mask, a Ti film, an Al film, and another Tifilm were formed by sputtering. After that, another resist mask wasformed, and the Ti film, the Al film, the other Ti film were patternedby dry etching. A mixed gas of BCl₃ and Cl₂ was used as the etching gas.Thus, a wire 73 (a source wire or drain wire of the TFT) was formed(FIG. 7B).

Measurement results of the TFT characteristics will be shown below.

A p-channel TFT will be described first. FIGS. 28A and 28B show draincurrent (ID)-gate voltage (VG) characteristics and mobility (μFE)-gatevoltage (VG) characteristics of the cases where the thickness of the Wfilm was 220 μm (FIG. 28A) and 170 nm (FIG. 28B). 1E-01 on the verticalaxis corresponds to 1×10⁻¹, 1E-03:1×10⁻³, 1E-0:1×10⁻⁵, 1E-07:1×10⁻¹,1E-09:1×10⁻⁹, 1E-11:1×10⁻¹¹, and 1E-13:1×10⁻¹³. This also applies toFIGS. 32A and 32B. Note that since the thickness of the TaN film was 30nm, the thickness of the whole gate electrode was 250 nm or 200 nm.

FIG. 29 shows ON-state current characteristics (Ion, gate voltage +10V,drain voltage +1V), FIG. 30 shows mobility characteristics (μFE (max),drain voltage +1V), and FIG. 31 shows threshold characteristics (Vth,drain voltage +1V); each of the measurement results is shown by circles.Further, number of a manufactured substrate (n) was set at 2.

Since the p-type impurity ions 65 were added over the gate electrode 63a while the first resist mask 62 a was left over the gate electrode 63a, the ON-state current characteristics, mobility characteristics, andthreshold characteristics did not change significantly even though thethickness of the W film forming the gate electrode was reduced to 220 nmor 170 nm. Accordingly, it is considered that when impurity ions wereadded, hydrogen ions did not penetrate a channel region 75 or that theamount of hydrogen ions penetrated the channel region 75 was not largeenough to affect the characteristics.

Next, an n-channel TFT will be described. FIG. 32 shows drain current(ID)-gate voltage (VG) characteristics and mobility (μFE)-gate voltage(VG) characteristics of the cases where the thickness of the W film was220 nm (FIG. 32A) and 170 nm (FIG. 32B).

FIG. 33 shows the ON-state current characteristics (Ion), FIG. 34 showsthe mobility characteristics (μFE_(—)1(max)), and FIG. 35 shows thethreshold characteristics (Vth); each of the measurement results isshown by circles.

The ON-state current characteristics, mobility characteristics, andthreshold characteristics did not change significantly even though thethickness of the W film forming the gate electrode was reduced to 220 nmor 170 nm.

P-type impurity ions (ions containing B) 65 were added over then-channel TFT while the second resist mask 62 b and the third resistmask 64 were left over the gate electrode 63 b. Meanwhile, n-typeimpurity ions 69 were added as n-type impurity ions (ions containingphosphorus) using the gate electrode 63 b as a mask. Accordingly, whenthe n-type impurity ions were added, penetration of hydrogen ions into achannel region 76 was a concern. However, the TFT characteristics didnot change significantly even when the thickness of the W film wasreduced as above. It is considered that the reason is because the n-typeimpurity ions were added at a lower acceleration than the p-typeimpurity ions or the n-type impurity ions were added at a less dose thanthe p-type impurity ions.

A comparative example will be explained below.

Similarly to the above embodiment, a p-channel TFT and an n-channel TFTwere manufactured. However, the gate electrodes 63 a and 63 b wereformed by using the first resist mask 62 a and the second resist mask 62b, and after making the gate insulating film thinner, the first resistmasks 62 a and the second resist mask 62 b were removed by ashing usingO₂. The W film 61 was 170 nm, 220 nm, 270 nm, 320 nm, 370 nm, 470 nm, or570 nm. Note that since the thickness of the TaN film was 30 mm, thethickness of the whole gate electrode was 200 nm, 250 nm, 300 nm, 350nm, 400 nm, 500 nm, or 600 nm.

Next, after forming the third resist mask 64 so as to cover thecrystalline silicon film 59 and the gate electrode 63 b, the p-typeimpurity ions 65 (ions containing B) were introduced into thecrystalline silicon film 58, thereby forming the source region 66 andthe drain region 67. Other than the steps described here, a p-channelTFT and an n-channel TFT were manufactured under the same conditions asthe above embodiment.

Measurement results of the TFT characteristics will be shown below.

A p-channel TFT will be described. FIG. 30 shows ON-state currentcharacteristics (Ion), FIG. 31 shows mobility characteristics (μFE(max)), and FIG. 32 shows threshold characteristics (Vth); each of themeasurement results is shown by circles. Further, number of amanufactured substrate (n) was set at 2.

Here, after the first resist mask 62 a over the gate electrode 63 a wasremoved, the p-type impurity ions 65 were added. Accordingly, when thethickness of the W film forming the gate electrode was less than 370 nm(when the thickness of the gate electrode is less than 400 nm in total),the ON-state current, and the mobility were found to decrease. Further,the threshold was found to shift on negative voltage side. This isconsidered to result from penetration of hydrogen ions into the channelregion.

As compared to the case where the p-type impurity ions 65 were addedwhile the first resist mask 62 was left over the gate electrode 63 a asdescribed above, TFT characters were found to deteriorate when the gateelectrode is made thin in the case where the first resist mask 62 a isnot formed over the gate electrode 63 a. That is, even if the thicknessof the gate electrode is 200 nm to 350 nm, penetration of hydrogen ioninto the channel region can be suppressed when the p-type impurity ionsis added while the first resist mask is left over the gate electrode.

An n-channel TFT will be described. FIG. 33 shows ON-state currentcharacteristics (Ion), FIG. 34 shows mobility characteristics (μFE(max)), and FIG. 35 shows threshold characteristics (Vth); each of themeasurement results is shown by circles.

Even when the thickness of the W film forming the gate electrode wasreduced to 220 nm or 170 nm, the ON-state current characteristics, themobility characteristics, and the threshold characteristics did notchange significantly.

This application is based on Japanese Patent Application serial No.2005-182156 field in Japan Patent Office on Jun. 22, 2005, the entirecontents of which are hereby incorporated by reference.

1. A method for manufacturing a semiconductor device, comprising thesteps of: forming a semiconductor film; forming a first semiconductorfilm and a second semiconductor film by processing the semiconductorfilm; forming a gate insulating film over the first semiconductor filmand the second semiconductor film; forming a conductive film over thegate insulating film; forming a first resist mask and a second resistmask over the conductive film; forming a first gate electrode over thefirst semiconductor film with the gate insulating film interposedtherebetween by processing the conductive film using the first resistmask, while forming a second gate electrode over the secondsemiconductor film with the gate insulating film interposed therebetweenby processing the conductive film using the second resist mask; forminga third resist mask so as to cover the first semiconductor film, thefirst gate electrode, and the first resist mask; forming a first sourceregion and a first drain region of the second semiconductor film by anion shower method with p-type impurity ions using the second resist maskand the third resist mask; removing the first resist mask, the secondresist mask, and the third resist mask after forming the first sourceregion and the first drain region of the second semiconductor film;forming a fourth resist mask so as to cover the second semiconductorfilm and the second gate electrode after removing the first resist mask,the second resist mask, and the third resist mask; and forming a secondsource region and a second drain region of the first semiconductor filmby an ion shower method with n-type impurity ions using the forth resistmask, wherein the p-type impurity ions are generated from diborane gasdiluted with hydrogen gas, and the n-type impurity ions are generatedfrom phosphine gas diluted with hydrogen gas or arsine gas diluted withhydrogen gas.
 2. A method for manufacturing a semiconductor deviceaccording to claim 1, wherein thickness of the gate insulating film is10 nm to 200 nm, thickness of the first and second gate electrodes is100 nm to 500 nm, and thickness of the first resist mask, the secondresist mask, the third resist mask, the fourth resist mask, and thefifth resist mask is 1.0 μm to 1.5 μm.
 3. A method for manufacturing asemiconductor device according to claim 1, wherein the gate insulatingfilm is a silicon oxide film, and the first and second gate electrodesare formed from a TaN film and a W film over the TaN film.
 4. A methodfor manufacturing a semiconductor device according to claim 1, whereinthickness of the first and the second gate electrodes is thinner than400 nm.
 5. A method for manufacturing a semiconductor device accordingto claim 1, wherein accelerating voltage of the p-type impurity ions ishigher than accelerating voltage of the n-type impurity ions.
 6. Amethod for manufacturing a semiconductor device according to claim 1,wherein accelerating voltage of the p-type impurity ions is 50 kV to 100kV, and accelerating voltage of the n-type impurity ions is 30 kV to 80kV.
 7. A method for manufacturing a semiconductor device according toclaim 1, wherein dose of the n-type impurity ions is less than dose ofthe p-type impurity ions.
 8. A method for manufacturing a semiconductordevice according to claim 1, wherein concentration of p-type impuritiesin the second semiconductor film is 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³, andconcentration of the n-type impurities of the first semiconductor filmis 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³.
 9. A method for manufacturing asemiconductor device, comprising the steps of: forming a semiconductorfilm; forming a first semiconductor film and a second semiconductor filmby processing the semiconductor film; forming a gate insulating filmover the first semiconductor film and the second semiconductor film;forming a conductive film over the gate insulating film; forming a firstresist mask and a second resist mask over the conductive film; forming afirst gate electrode over the first semiconductor film with the gateinsulating film interposed therebetween by processing the conductivefilm using the first resist mask, while forming a second gate electrodeover the second semiconductor film with the gate insulating filminterposed therebetween by processing the conductive film using thesecond resist mask; forming a third resist mask so as to cover the firstsemiconductor film, the first gate electrode, and the first resist mask;forming a first source region and a first drain region of the secondsemiconductor film by an ion shower method with n-type impurity ionsusing the second resist mask and the third resist mask; removing thefirst resist mask, the second resist mask, and the third resist maskafter forming the first source region and the first drain region of thesecond semiconductor film; forming a fourth resist mask so as to coverthe second semiconductor film and the second gate electrode afterremoving the first resist mask, the second resist mask, and the thirdresist mask; and forming a second source region and a second drainregion of the first semiconductor film by an ion shower method withp-type impurity ions using the forth resist mask, wherein the p-typeimpurity ions are generated from diborane gas diluted with hydrogen gas,and the n-type impurity ions generated from of phosphine gas dilutedwith hydrogen gas or arsine gas diluted with hydrogen gas.
 10. A methodfor manufacturing a semiconductor device according to claim 9, whereinthickness of the gate insulating film is 10 nm to 200 nm, thickness ofthe first and second gate electrodes is 100 nm to 500 nm, and thicknessof the first resist mask, the second resist mask, the third resist mask,the fourth resist mask, and the fifth resist mask is 1.0 μm to 1.5 μm.11. A method for manufacturing a semiconductor device according to claim9, wherein the gate insulating film is a silicon oxide film, and thefirst and second gate electrodes are formed from a TaN film and a W filmover the TaN film.
 12. A method for manufacturing a semiconductor deviceaccording to claim 9, wherein thickness of the first and the second gateelectrodes is thinner than 400 nm.
 13. A method for manufacturing asemiconductor device according to claim 9, wherein accelerating voltageof the n-type impurity ions is higher than accelerating voltage of thep-type impurity ions.
 14. A method for manufacturing a semiconductordevice according to claim 9, wherein accelerating voltage of the n-typeimpurity ions is 50 kV to 100 kV, and accelerating voltage of the p-typeimpurity ions is 30 kV to 80 kV.
 15. A method for manufacturing asemiconductor device according to claim 9, wherein dose of the p-typeimpurity ions is less than dose of the n-type impurity ions.
 16. Amethod for manufacturing a semiconductor device according to claim 9,wherein concentration of n-type impurities in the second semiconductorfilm is 1.0×10¹⁹ cm⁻³ to 1.0×10²¹ cm⁻³, and concentration of the p-typeimpurities of the first semiconductor film is 1.0×10¹⁹ cm⁻³ to 1.0×10²¹cm⁻¹.